Unit 4 Blog Reflection -- Jan.

Part A.) WHAT WE LEARNED

1.) Circular Motion (tan/rot Velocity); Gears; Train
2.) Rotation Inertia & Angular Momentum; Hoop/Ball
3.) Conservation of Momentum; Skater; RI versus RV
4.) Torque
5.) Center of Mass & Center of Gravity; Sports
6.) Centripetal Force (and centrifugal)
7.) Extra Problems to Consider


A1.) Circular Motion (tan/rot Velocity)

Linear Speed is exactly the same as Tangential Speed. The equation in words is "the direction of motion is tangent to the circumference of the circle or rotational axis per time interval."

• Formula: distance/time

Rotational Velocity is completely different. It is the amount of rotations an object or system makes in a certain time interval.

• Formula: rotations/time

Two things can have the same tangential velocity but different rotational velocities.  Two gears may cover the same distance over a period of time, but they don't have the same # of rotations.
A smaller gear would have to rotate maybe twice as many times as the big gear rotates to cover the same tangential distance.

Similarly, train wheels keep a train on the tracks --> The wheels are slanted with the bigger (larger radius) side on the inside of the track, while the smaller side is on the outside. This makes the larger side have a higher tangential velocity because it has to cover more distance to catch up.
The wheels will tend to rotate towards the middle of the track; the larger side covers more distance per revolution and it turns. They re-align and on turns, the train can straighten-up.


A2.) Rotation Inertia & Angular Momentum; Hoop/Ball

Rotational Inertia is a branch of inertia that states an object will resist change in rotation, whether it be to start or stop the rotation.
What determines how much inertia an object has is the distribution (position) of its mass. When more of the mass is further away from the axis of rotation, there is more inertia; it will be harder to start/stop its spin. When the mass is closest to the axis of rotation, the object will be easier to start/stop its spin.

The hoop and ball: Explained here in this podcast video, a hoop and a solid cylinder race down a ramp. Both have the same mass and radius. Why does the hoop lose? Look below!


 
Angular Momentum is the rotational inertia multiplied by the rotational velocity of an object. These terms are inversely proportional, so as one gets big, the other gets smaller. Vice-versa.

• Formula: RI x RV

A3.) Conservation of Momentum

The conservation of momentum occurs when an object is rotating, such as a ice-skater. Let's say that she has her arms out, and suddenly pulls them in toward her body. What happens?
At first, her arms are far from her axis of rotation, so she had a high rotational inertia and a low rotational velocity (formula).
But as her arms go in, she spins faster! Her rotational inertia is low and so her rotational velocity must get higher to compensate for the change. As one goes up --> the other goes down.

In this picture, the "I" stands for rotational inertia. The "w" stands for rotational velocity.

BOTH girls in the picture has the same angular momentum because RI x rv = ri x RV.

A4.) Torque 

Torque is a force that causes rotation. 

• Formula: force x lever arm

A force is a push or a pull on an object.

A lever arm is just the distance between the force-action and the axis of rotation. The lever arm is perpendicular to the force.

So as the formulas shows us, the force and the lever arm are directly proportional. Whichever gets larger helps raise the torque and cause a rotation of some sort.

Let's do a torque problem: There's a 2N ball and a ball that is 3N resting on a balance with a fulcrum in the center. The 3N ball is 4 meters from the axis of rotation. How many meters (how long is the lever arm) is the 2N ball from the center?

clockwise torque = counterclockwise torque
(force)(lever arm) = (force)(lever arm)
(3N)(4m) = (2N)(x)
x = 6 meters


A5.) Center of Mass & Center of Gravity; Sports

Center of Mass: the point where the average distribution of mass is located on an object (the middle usually).

Center of Gravity: the point where gravity is pulling down an an object.

Base of Support: the foundation on which an object is located, right above the support force.

Why are football players less likely to be pushed over when they keep their legs should-width vs. feet together? 
~ With legs further apart, the base of support is widened, giving a larger foundation for the object. It is harder for the center of gravity to go beyond the base of support. When it does go over, however, the object will fall.

Why are wresters told to bend their knees when wrestling?
~ They bend their knees so that their center of mass is lower to the ground (and base of support), so it is harder to get the center of mass beyond the base support and it would be unlikely for the wrester to fall over sideways.


A6.) Centripetal Force (and centrifugal)

Centripetal Force: center-seeking force (toward the axis of rotation).

Centrifugal Force: center-fleeing force; it is FICTICIOUS (away from the axis of rotation).

This image is of a ball rotating in a circle. The centripetal, centrifugal (fictitious), path of inertia (tangent line), and center are all labeled.

A7.) Extra Problems to Consider

• Bus problem: you hit person next to you as the bus turns a sharp left...why?
• Satellite: is the satellite stationary above earth? How do the forces/vector quantities keep it in orbit?
• Why does water fly out of a washing machine? Is the water moving on a curved or straight-line path?
• Why are racetracks banked with one edge higher than the other? Where is the centripetal force acting on it? Add vectors to prove your answer.

Part B.) REFLECTION AND CONNECTIONS

What I've found difficult about this unit is the last topic we studied: centripetal force. I understand the problems and have contributed in class, but I needed more time to study it.

I overcame this difficulty by using my quizzes and notes to re-write the answer and descriptions of each term and each problem we did together. It helped be see physics not just on paper, but also in my head.

My effort in this class has been right on target. I do my homework and participate every day, because the material is interesting and my classmates help each other. The formula/problem-solving questions are fine for me; I do each step carefully and end up with the right answer (unless I did math wrong or didn't have persistence!)

My goal for the next unit is to be better organized with my quizzes and other scattered papers. Right now, I have everything in my spiral notebook and the inside cover of my binder. Also, I want to start doing more things with other people in my class, that I don't typically talk to every day. I am excited for the next chapter!

~ Connections

• My desk dresser is a small, rolling 2-drawer cabinet. All my of my school-supplies is in there, and when I open the drawer, the dresser falls over! I recognized that its center of mass had been shifted, and was beyond the base of support. 
• Just like an ice-skater, I rollerblade. Whenever I spin in circles with my arms spread out, I slow down, but when they are tucked in, I spin faster!
• Lastly, I was opening my dorm room door. My hand acted as the twisting force, and my fingers the lever arm. The door knob turned and my door opened. I actually noticed the door-stop as well.

CHEERS.

Mass of a Meter Stick -- Torque Lab

Step 1 DEMO:

The meter stick was not balanced on the edge of the table and either fell, or was not actually in a balanced state, meaning that the torques of both sides of the stick were not equal. What is torque? It is the amount of force multiplied by the lever arm that ultimately creates a rotation of the system. The meter stick is the rotation in this lab.

After speculation, (the meter stick balanced at approximately 50cm) we took the meter stick and added a 100gram weight on the end. Once it was steady, the next goal was to balance the stick again, and measure the distance between the weight/(end off the table) and where the axis of rotation was. The lab asked for pictures labeling the center of gravity, the lever arm, and the force.

Step 2 PLAN: 

The equation we used to solve for the meter stick’s mass was derived from the idea that the torque on either side was equal when balanced. Because torque is force times distance, simply put, the new equation was (Fgravity)(distance) = (Fgravity)(distance). Fgravity, we learned in chapter 2, is the same term as weight, which equals (mass)(gravity).

Now: (mass)(gravity)(distance) = (mass)(gravity)(distance)

(0.1kg)(9.8)(30.5cm from table) = (x)(9.8)(19.5 from end of table to 50cm mark)

x = 0.156 kg  OR  156 grams

Percent error: (156 – 150.7) / 150.7 = 3.5% error!!

         

SUMMARY & Explanations – The method that worked…using Mr. Roo as a resource.

*Torque:  what makes an object or system rotate; (force)(lever arm)

*Lever arm:  the distance from the axis of rotation; more distance, easier to rotate

*Force:  a push or a pull on an object; Fgravity is just the weight

*Center of Mass:  where an object’s mass is in relation to the pull of gravity ¯

*Mass:  how much matter an object has

*Weight:  the force of gravity on an object’s mass

Why things are balanced: the torque is equal on either side of a rotating object/system. The bigger the lever arm, the less force is required to rotate the object. The smaller the lever arm, the more force is needed to rotate it. They’re inversely proportional.  

Here are some pictures I made from PowerPoint:

    

   CHEERS.

Torque -- Ch. 8 Resource

We've all been on a see-saw. Well, I hope so. If you haven't, they are fun but dangerous park additions that require 2 people: one on each end. Here's a picture to clear things up.

One person sits on the left end, and another on the right. But if they're masses are not equal, the lever won't be even. The website I found embedded below provides an easy example of torque and how we find it in everyday life. 

Torque = "the product of the rotational force exerted at right angles on the lever, times the distance between the point of force and the fulcrum" (dsc.discovery.com).

• (Torque = force x distance from axis)

http://dsc.discovery.com/tv-shows/mythbusters/about-this-show/physics-of-seesaws.htm

CHEERS.

Angular Momentum -- Ch. 8 Resource

This video is focusing in on how a cat lands on its feet. It is upside-down, then flips over so quickly that it lands on all fours. But how? Look and see--





The cat pulls its legs in towards its body, or axis of rotation. This causes its rotational velocity to increase, allowing for the cat to flip fast enough before landing. However, the cat's rotational inertia is less, so it is easier to [start to] rotate.

Angular momentum = Rotational Inertia x Rotational Velocity.

• RI and RV are inversely proportional: when one increases, the other decreases.

An object has less rotational velocity if the most mass is distributed furthest away from its axis of rotation. It also has more rotational inertia because it is harder to start/stop/continue spinning.

An object has more rotational velocity if the most mass is distributed closest to its axis of rotation. It also has less rotational inertia because it is easier to start/stop/continue spinning.

Hope you enjoyed,

CHEERS.

Unit 3 Blog Reflection -- Dec.

Part A: What We Learned 

1.) What is Newton's 3rd Law? Action/Reaction Pairs

2.) Tug of War; Horse and Buggy Problems

3.) Adding Forces/Vectors with Angles

4.) Gravity and Tides

5.) What is Momentum? Relationship with Impulse

6.) Conservation of Momentum

A1.) N's 3rd Law; Action/Reaction Pairs                                                                                                                    

Newton's 3rd Law states that "every action and has an equal and opposite reaction." 

Here are some examples:

• Road pushes tire forward, tire pushes road backward.
• Rocket pushes gas backward, gas pushes rocket forward
• Girl pushes water backward, water pushes girl forward.

Now-- to make a correct pair, we must keep the action the same, and also the subjects; the direction is the opposite!

Action/Reaction with Different MASSES:

• Cannonball shot out of cannon
• Cannonball: F = m*a
• Cannon:       F = m*a

A2.) Horse and Buggy & Tug of War!                                                             

So if the forces are equal and opposite, why don't the forces cancel to zero? Well....you have to look at the entire system involved in the situation. The horse and buggy provide a great example for understanding the concept of a system of forces:

http://www.batesville.k12.in.us/physics/phynet/mechanics/newton3/Images/HorseCart0.GIF

The image shows a horse pulling a buggy. Both are on top of the road. If Newton's 3rd Law is true, why do they move forward?

• Label the action/reaction pairs first.
• Horse pulls buggy forward, buggy pulls horse backward.
• Horse pushes ground backward, ground pushes horse forward.
• Buggy pushes ground backward, ground pushes buggy backward.
• The arrows representing the forces of the horse/ground should be longer than those of the buggy/ground. This is because the horse exerts more force.
• Summing it up,  the horse pushes harder on the ground, moving itself forward, than the buggy does. Therefore, the system moves.

Tug of War is the same concept of Newton's 3rd Law. Whichever person pushes harder (exerts more force) against the ground wins in this case:

http://www.bbc.co.uk/bitesize/standard/physics/images/tug_of_war.gif

A3.) Adding Forces/Vectors with Angles                                                         

Before going over this sub-topic, let's watch the podcast to get a view of things:




I used Powerpoint (screenshots of slides) and iMovie to create this review.

The main uses/functions of adding vectors are:

• Box and ramp (or snowboarder and slopes)
• Boats and current (or airplane and wind)
• Rope tension and ball
• Pool balls

A4.) Gravity and Tides!                                                                         

[Everything with mass attracts all other things with mass]

What does the force of gravity depend on?
-- mass of objects (F_g ~ m) 
-- distance between objects (F_g ~  d²)

The "Universal Gravitational Formula" is what we use to find the Force of Gravity:

F = G*m1m2
           d²

Tides are those wave-things you see on the ocean's shore when you go on vacation. 
 *Correction: they are caused because of the difference in force felt by opposite sides of the Earth.

There are 2 high tides and 2 low tides during an entire day or 24 hour period. (6 hours apart).

http://4.bp.blogspot.com/-0OCrG-5Cv-0/UGtb75p3BNI/AAAAAAAAABs/N85TYJ4l-yo/s1600/SpringNeap-Tides-color.gif

Spring Tides: highest of high tides/lowest of low tides; just after new or full moon

Neap Tides: moderate; least difference between high and low tides; just after 1st/3rd quarters

~ Practice problems:

• When the distance between 2 objects is doubled, what is the resulting force?
• When the distance between 2 objects is halved, what is the resulting force?
• When the distance between 2 objects is quadrupled, what is the resulting force?
• When the distance between 2 objects is cut in 1/3, what is the resulting force?

*Answers:

• F = cut in 1/4
• F = quadrupled
• F = cut in 1/16
• F = tripled

A5.) What is Momentum? Relationship w/ Impulse                                         

Momentum is "inertia in motion" or the (mass*velocity) of an object.

P = mv [units: kg*m/s]

EX: A 10kg ball is moving at a speed of 5m/s. What is its momentum?

       P = mv

       P = (10)(5)

       P = 50 kg*m/s

Impulse is "force on a time interval" or the (force*change in time) of an object.

J = FΔt [units: N*s]

J = ΔP, therefore

ΔP = FΔt 

• Increasing momentum -- greatest force for as long as possible
• Decreasing momentum -- stopping a moving object by way of haystack or wall
• Decreasing momentum over a short period of time -- punching someone; the amount of time determines the force.
• J = F*t
• J = F*t

How does an airbag keep you safe?

• No matter how the person is stopped, he/she is going from moving to not-moving.
• P=mv
• The change in momentum is the same regardless of how the person is stopped.
• ΔP = Pfinal - Pinitial
• Because the ΔP is zero, (Pfinal is always zero), Impulse must also be zero.
• J = ΔP
• The airbag stops the person over a longer period of time. This causes the force on the person to be smaller. 
• J = F*t
• J = f*T
• The smaller force results in the person not being injured. 

A6.) Conservation of Momentum                                                            

mV = Mv (inversely proportional)

"In the absence of an external force, the momentum of a system remains unchanged."

Elastic Collision: objects bounce off each other

Inelastic Collision: objects stick to each other

~ There are 2 formulas we learned in class: one for each type of collision...

• m_av_a + m_bv_b = m_av_a + m_bv_b 
• m_av_a + m_bv_b = m_av_a (V_ab)

~ We plug in the velocities before and after to find the final velocity!

OPPOSITE MEANS NEGATIVE DIRECTION;

ONE VELOCITY WILL ALWAYS BE NEGATIVE IN THESE PROBLEMS!

Which exerts more force: an ball that bounces off a person's head, or a ball that sticks to a person's head? Which will hurt more? Why?

-- When the ball bounces, it changes momentum twice. Once to stop, and once to start moving again.

-- Therefore, its impulse is double, and it exerts twice the force. 

-- The bouncing ball will injure the person more. Sorry!

Difficulties and How I Overcame Them                                                     

I thought the tides were hardest to understand because it is confusing to know why and how the water level of the ocean changes and when. The gravitation force was alright, but I wish we'd had some tides review going into making this reflection.

Also, labeling the Fnet, Fsupport, and Fweight on each vector diagram lost me points on quizzes. I hope to practice this before the test.

I overcame these difficulties by doing textbook practice problems for help and homework. I got more and more familiar with the topics and feel good about the problem-solving! That's what made the lightbulb click!

Problem Solving Skills, Effort, and Learning                                              

My ability to solve and work on mathematical problems and critical thinking in this class has improved as the semester has progressed. I usually enjoy contributing to class discussions and helping my table-classmates with the warm-ups. 

My effort has been guided by my desire to do well and master the material. 

My goals for the next unit are to be more of a presence in class even if I am not fully engaged. I will do this by entering the room prepared and ready to learn. Also, I want to have a great time with my 5th form friends.

Part B: Connections                                                              

On my Thanksgiving Break, I noticed the tides each day. On the airplane, I thought of the gas pushing plane forward and plane pushing gas backward. I thought of the gravitational pull on me at sea-level. 

The current and boats problem, tug-of-war (I played on the beach and won!), and airbag problem are influential to my life and anyone's life.

I look forward to learning more physics that is applicable to my life.

CHEERS.

Tides -- Newton's 3rd Law Resource

WHO LIKES THE BEACH? I PREFER THE LAKE, BUT IT'S MY OPINION.

So I'm sure many of you have used this video as a resource. Well, while we're talking about tides, let's mention some of the good stuff.

First off: "Everything with mass attracts all others things that have mass."

What we know is that the Force of gravity is inversely proportional to the distance between the objects. As they get further apart, the force is less, as the distance decreases, the force increases.

Tides - definition: Tides are caused because of the difference in force felt by opposite sides of the Earth.

There are 2 high tides and 2 low tides a day (every 24 hours). Each is 6 hours apart.

• Spring tides are when the sun, Earth, and moon line up. The highest and lowest tides (more/less than usual) occur. *Full & new moon*
• Neap ties are just after the first or third quarters of the moon occur. *Such as a gibbous moon or crescent*

VIDEO~ by minutephysics



He draws the forces acting on the moon with arrows, which helps! At 0:18 seconds, he draws both sides of the pull. Newton's 3rd Law proves that "the close side of the Earth gets pulled away from the middle, which in turn gets pulled away form the far side."
Ex:  <--- O --->

Gravity is weaker at a greater distance, and in the video, he draws a hose and sheep. I like this image a lot!

His last [proposal/theory/awesomeness] is that by the year 270000000000, "a day and a lunar month will each have the same length: about 50 of our current days."

TALK ABOUT A LONG DAY.

CHEERS.

Unit 2 Blog Reflection -- Oct.

Part 1A: What we learned

1. Newton's 2nd Law of Motion
2. Newton's 2nd Law Lab
3. Skydiving
4. Free Fall - General
5. Free Fall - Throwing things straight up
6. Free Fall - Throwing things straight down
7. Free Fall - Falling at an angle
8. Free Fall - Throwing things up at an angle

#1.)

Newton's 2nd Law in words is "Force is directly proportional to acceleration and inversely proportional to mass. (F~a), (F~1/m).

Weight is the force of gravity on an object's mass. 

Mass is the amount of matter in an object / also a measure of inertia. 

Formula: Weight = Mass * Gravity (W=mg)

Gravity is always 9.8m/s² unless we are solving problems, which is when we simplify it to 10m/s². 

EX: A box is pushed to the left 30N and to the right 10N. The force of gravity on the box's mass, (weight) is 200N downward. What is the box's mass and acceleration?

w=mass*gravity            a=net force/mass

200=m(10)                    a= 20/20

m= 20kg                        a= 1 m/s²

We solved for the mass first, then plugged the 20kg into the other equation to find the acceleration!

EX: If the mass of a system is kept constant and the force of the system is doubled, what happens to the acceleration? Let's use some numbers:

• f=ma
• 6=2*3
• 12=2*?
• a=6, it doubled.

#2.)

Newton's 2nd Law Lab: cart, hanging weight, pulley/string, discs (extra mass).

Experiment A...

-- We kept the force of the system constant throughout this part of the lab. By adding masses to the cart each time by 0.1kg, we used the computer to see how the acceleration varied.

-- The acceleration decreased because as more mass added to the system, less force acts on it. (Inversely proportional).

As the mass increased, the acceleration decreased.

The force of the system remained constant.

-- To calculate the force on the system, use w=mg and plug in "mass of system" and "gravity."

Experiment B...

-- We kept the mass of the system constant throughout this part of the lab. By removing masses from the cart to the hanging weight each time by 0.1kg increments, we used the computer to see how the acceleration varied.

-- The acceleration increased because the more mass added tot he hanging part, the more weight, (force of gravity on the object's mass). Which means more force!

As the force of the cart increased, the acceleration increased.

The mass of the system remained constant.

Using y=mx+b:

Newton's 2nd Law: a = Fnet * 1/Mass

                                y = m     * x

The equations line up! Whatever variable is kept constant is the slope (m). The "y" is usually acceleration, as we observed this after changing the force and mass of the system. The "x" is either the force or 1/mass depending on the experiment.

To confirm N's 2nd Law, we can use the slope (a number) and compare it to what the calculated/predicted number was. If they differ by less than 10%, it is verified. If not, there is an issue.

#3.)

Skydiving: we spent a good chunk of time looking at and understanding what goes on in skydiving and how it relates to N's 2nd Law. Here are some things that we need to know at the start:

• Terminal velocity is when the force of air resistance (Fair) equals the force of gravity on the diver's mass (Fweight).
• At terminal velocity, because the net force is 0Newtons, the acceleration must be 0m/s². It's in equilibrium.
• At terminal velocity, the diver is at his/her maximum speed, which is constant.

Speed and Surface Area are directly proportional to the Fair. So, the more speed an object gains, the more air resistance. Same with the surface area of something such as a parachute.

Paul G. Hewitt's drawings (practice page handout) are a good visual of the entire motion. 

- Bronco, the diver, falls out of a helicopter at a time of 0 seconds, with no Fair, and his velocity is least here, which shows us that his acceleration is most. 

- Next, as Bronco continues to fall (1000N Fweight) the Fair gradually gets bigger because he gains speed over time. His acceleration decreases because the net force decreases. 

- As he reaches terminal velocity, his net force and acceleration are 0. The velocity is constant.

- When Bronco pulls the parachute, his Fair gets big because of the increased surface area. His net force, (now negative and upward), makes the acceleration both negative and upward. His velocity is still downward though!

- After the parachute is pulled, Bronco's Fair is most. His net force is least, and his acceleration is least.

- Once he regains terminal velocity by slowing down (the whole purpose of a parachute), his net force and acceleration are 0. The velocity is now constant.

The terminal velocity before the parachute is opened is much higher than after, because of the slower speed due to the increased surface area and more Fair.

#4.)

Free Fall - General explanations.

Free fall is when the only force acting on a falling object is the force of gravity.

The formulas for vertical distance, time, and velocity are as follows:

• d=1/2at²
• v=at

Because the only force is gravity (10m/s), the ball (object) accelerates at 10m/s² each second.

When it falls, the ball is at t=0seconds and velocity=2m/s.

At 1 second, the ball's velocity is 10m/s and its acceleration is 10m/s² still.

At 2 seconds, the ball's velocity is 20m/s and its acceleration is 10m/s² still.

At 3 second, the ball's velocity is 30m/s and its acceleration is 10m/s² still.

After 3 seconds, it lands. How do we calculate the vertical distance from the ground at each second?

d=1/2(a)(t²)

d=1/2(10)(3²)

d=45 meters high / total!

After 1 second, the ball is 

d=1/2(a)(t²)

d=1/2(10)(1²)

d=5 meters high off the ground.

We can use what we know for each second.

#5.)

Free Fall - Throwing things straight up.

When thrown up, the ball must have an initial velocity (not 0m/s). No Fair.

The time starts at 0 seconds.

It is the same concept as being thrown down, but in the opposite direction.

After each second, the velocity decreases by 10m/s, even though the acceleration is 10m/s² still.

At the top of its path, the ball's velocity is 0m/s. 

We can look at a picture and see the time it takes to go up, down, and add them to get the total time in the air.

To use d=1/2(a)(t²), we must plug in the time it takes to go up. We can get the vertical distance. 

We can also use v=at to find the velocity/time depending on what we are given!

If the question asks "how far from the ground is the ball after 5 seconds," we must find the distance from the top of the ball's path to that second, and subtract it from the total vertical distance.

#6.)

Free Fall - Throwing things straight down

When thrown down, the ball's initial velocity is not 0m/s. The acceleration is 10m/s² still.

The time starts at 0 seconds.

It is the same concept as being thrown up, but in the opposite direction.

After each second, the velocity increases by 10m/s.

This is the same concept as throwing things straight up, but the velocity increases.

We can use d=1/2(a)(t²) to find the distances.

THE ONLY THINGS THAT DETERMINES HOW LONG AN OBJECT IS THE IN THE AIR IS THE VERTICAL DISTANCE.

#7.)

Free Fall - Falling at an angle

EX:  Let's say that a plane 125 meters high drops a box while it is moving at a constant horizontal velocity of 90m/s. 

• Everything is the same in Free Fall with the time at 0 seconds, no Fair, and The acceleration is 10m/s² still.
• We can plug 125m into the equation d=1/2(a)(t²) to find the time. 5 seconds.
• Drawing a picture for help, we want to find the horizontal distance now. Using v=d/t, we plug in 90m/s and 5 seconds to get out 450meters.
• The horizontal velocity,time, and gravity NEVER change.

Sometimes we want to find the actual velocity of the box at a certain point. After 2 seconds, the box should be at a vertical distance (from the top) of 10 meters and a horizontal distance of 180 meters. 

-- Even though the numbers are not the same, we use a² + b² = c². Then we get the actual velocity looking at the right triangle.

Here is my podcast!

#8.)

Free Fall - Throwing things up at an angle

EX: Let's say that an object is thrown up at a 45-degree angle and has a velocity of 20m/s in the horizontal direction, and 40m/s in the vertical direction. Look below.

a. How long will it be in the air total?

b. How fast will it be moving at the top of its path?

c. How far downfield will it go?

a~ It starts with 40m/s in the vertical direction, so after 4 seconds, it'll be at the top (and 4 seconds to go down) = 8 seconds total.

b~ The horizontal velocity never changes = 20m/s.

c~ v=d/t

  20=d/8

   d=160 meters

#BONUS.) Extras!!!!

• A high-speed jet flies really high in the air. When it flies exactly over you, it drops an object. If you don't move, will it hit you? Why or why not?
• What is the square root of 2? How does this help us?
• We know that force is directly proportional to acceleration and inversely proportional to mass, but why? It'll be nice if you know this.
• If you drop a lead ball and a ping pong ball for the same height at the same time? Which one will hit first and why? What if they are at a super high distance form the ground? 
• In the absence of air resistance, why do a feather and a penny hit the ground at the same time if dropped fro equal heights at the same time?

Part 2A: Difficulties, help, effort, skills, etc.

The most difficult idea that I had issues with was the idea that "what happens to an object's velocity if it is traveling with a decreasing acceleration?" This question was on the quiz, and I missed it. I understand it now though!
Also, the Newton's 2nd Law Lab was scattered. The 2 different experiments were separate, but the analysis after, which confused me tons.

I overcame these difficulties by asking about them in class. Drawing pictures and memorizing the formulas/constants really helped.

My effort has been consistent, and I am glad that the class has been going well for me thus far. I like the other students in the class and we help each other. The dynamic is great until someone goofs off and I can't focus. My problem solving has improved! 

My goals for the next unit are to:
- Stay attentive in class and be active when learning about new topics.
- Keep up my grade and try hard, even if it leads to failure.
- Persevere and stay positive no matter the consequences, because a good attitude is necessary.
- Attempt not to breeze through, but to challenge myself more.

Part B: Connections

Newton's 2nd Law of Motion can be found everywhere. Anything that is thrown, dropped, rolled, pushed, forced, or acted upon...will move. We can visualize the relevance to our topic - acceleration, force, and mass.

Just the other day, I threw a water bottle upward at an angle (to a friend during swim practice), and he caught it. I thought about the gravity and the velocity and how they worked together.

Looking forward to the next unit--

CHEERS.