FarleyPhysics.com

1. Momentum demonstration and explanation.

2. Momentum video

3. Momentum lab
Use the momentum applet here to answer the following questions. Be sure to draw each impact in your notes and include all questions and answers.

1. Press reset and then start. Watch the number for total momentum for the entire interaction. What is the total momentum? Does the total momentum change? Calculate the momentum of mass 1 and mass 2 (p = mv) before the impact and after the impact.

2. Set the speed of mass 2 to zero, press reset to reset the position, and then start the simulation. What is the momentum of mass 1 and mass 2 before the impact? What is the momentum of mass 1 and 2 after the impact? Where did mass 1′s momentum go? Does the total momentum ever change?

3. Set each mass to 2, and Speed 1 to 2 and Speed 2 to -1. What is the momentum of mass 1 and mass 2 before the impact? What is the momentum of mass 1 and 2 after the impact? Where did mass 1′s momentum go? Does the total momentum ever change?

4. Set the elasticity to zero. Set both masses to 1 and speed 1 to 1 and speed 2 to -1. Calculate the momentum of mass 1 and the momentum of mass 2 before starting the simulation. Add them together to find the total momentum. Now run the simulation. Describe what happens in terms of the conservation of momentum.

5. With elasticity still at zero, set Speed 2 to zero, mass 1 to 2 and mass 1′s velocity to 2. Calculate the momentum of each mass before the impact. Run the simulation and describe what happens.

6. Play the Sumo Wrestling Game and see who can win.

1. Return and discuss quizzes

2. Free Body Diagrams

In groups of 3 or less, split the provided paper into six sections (two columns, 3 rows)

On the left, draw a picture of what is happening and a description of what is happening in large letters. On the right draw the corresponding free body diagram and clearly label all the forces (ignore air, friction, other small forces).

Left side: A projectile flying through the air. Right side: free body diagram showing all the major forces acting on the projectile.

Left side: A car hitting a wall. Right side: free body diagram showing all the major forces acting on the car.

Left side: A ball being kicked. Right side: free body diagram showing all the major forces acting on the ball.

Go around and put a star on correct free body diagrams. After your drawings are checked, draw them into your notes. If your drawings have mistakes, find a correct diagram and draw it into your notes.

Projectile Motion Simulations 2

For today’s lesson, you will go to the following website:

http://www.physicsclassroom.com/class/vectors/U3L2a.cfm

Answer the following questions based on your reading of the pages and doing the simulations.
1. What is a projectile? Give three examples of projectiles and draw them.
2. What is the only force acting on a projectile?
3. Draw the free body diagram for a projectile.
4. If you knew the mass of a projectile, what would be the force on the projectile? (you wont find this on the site, you need to figure it out yourself)
5. Is force required to keep an object in motion? Which law explains this?
6. Gravity only effects what motion (vertical or horizontal) of a projectile?
7. Draw the path of a projectile with gravity turned off and gravity turned on.
8. Click the “Animation” button on the first page. In the absence of gravity, where should you aim the banana in order to hit the monkey?
9. With gravity turned on, where should you aim the banana? Look at the aiming above the monkey animation and the aiming at the monkey animations at the bottom of the page.
10. If you are going to throw the banana very slow, where should you aim it? What limits how slow you can throw the banana?

There are five animations on THIS PAGE. Answer the following questions while watching them:
11. For the horizontally launched projectile, how does the velocity in the x direction change over time and how does the y velocity change?
12. For the projectile launched at an angle, how does the velocity in the x direction change over time and how does the y velocity change?
13. For the truck driving under a projectile, why does the ball always stay right above the truck? Draw a picture showing this. How do you think air resistance would effect this?
14. For the airplane dropping a package, why does the package always stay under the plane? Draw this. How would air resistance effect what happened?

Quiz 7

1. Return and discuss Quiz 6

2. Equations of motion problems:

A car initially traveling at 5 m/s accelerates for 10 seconds at 5 m/s^2 How far does the car travel in this time? How fast is the car traveling after that acceleration? If the car’s mass is 1000kg, what is the net force on the car?

A bus initially traveling at 20 m/s accelerates at 5 m/s^2 for 2 seconds. How fast is the bus now going? How far does the bus travel in that time?

A rocket with a mass of 10,000 kg accelerates at 22 m/s^2 for 90 seconds. What is the force exerted by the rocket engine? How fast is the rocket moving after this time? How high has the rocket gone after this time?

You push a 50 kg block with a force of 25 N. What will the block’s acceleration be? If you push the block with this force for 5 seconds, how fast is the block moving? How far from the starting point will the block slide?

A rocket traveling at a constant speed of 1000 m/s for 4 seconds has what acceleration? What is the force exerted by the engine? How far does the rocket travel in this time?

Today you will study projectile motion. At the end of the day you should know the angle to launch a projectile if you want it to go the furthest, the angle if you want it to go the highest, and what air resistance will do to the distance it goes.

Use the following simulation to answer the questions.

http://galileoandeinstein.physics.virginia.edu/more_stuff/Applets/ProjectileMotion/jarapplet.html

1. Find the angle that a projectile should be launched for it to go the longest distance away from where it was launched. Draw a picture in your notes of the Height vs. distance graph with the furthest distance.

2. Find the angle that makes the projectile go the highest. Draw a picture of Height vs. distance for this.

3. Add air resistance and explain what happens to the distance a projectile can go with air resistance vs. without air resistance. Draw a picture showing both and label the path with air resistance and without.

4. Turn air resistance off and change the mass. What happens to the distance a projectile goes as you increase mass?

5. Turn air resistance on and change the mass. What happens to the distance as you change the mass when there is air resistance?

Third Motion Equation

1. Examples

2. Work the following problems:

1. A car travels at 25 m/s for 5 seconds. How far does the car travel?

2. A car starts at rest and accelerates at 10 m/s^2 for 5 seconds. How far did the car travel in this time?

3. A car initially traveling at 25 m/s accelerates for 5 seconds at 5 m/s^2 How far does the car travel in this time?

4. A rock falls from rest for 4 seconds. How far does it fall in that time?

5. If you throw a rock downward at 10 m/s, how far will the rock fall after 3 seconds?

6. If a train travels 2000 meters at 25 m/s, how long does it take?

7. If a train starts from rest and accelerates at 2 m/s^2 for 200 seconds, how fast will it be going and how far will it travel in this time?

8. A rocket launches from rest with an acceleration of 20 m/s^2 (2 g’s). If the rocket engines stay on for 90 seconds, how fast is the rocket moving after this time and how far up has the rocket risen?

Equations of motion

V = x/t
V = Vo + at
X = Xo + Vot +(1/2)at^2

1. Solving the first two for any value.

2. Examples of using them

3. Questions:

For each question, 1) list the values given and the value needed. 2) write the equation you will use. 3) Solve the equation for the value needed 3) Substitute the values given and solve.

You walk 20 meters in 40 seconds, what is your speed?

You throw a rock downward with a velocity of 10 m/s. After 2 seconds, how fast is it moving? What is its acceleration after 2 seconds?

A car travels down the road at 5 m/s for 30 seconds. How far does the car go?

A rocket travels 2000 meters at a velocity of 25 m/s. How long does it take?

A bus initially traveling at 20 m/s accelerates at 5 m/s^2 for 5 seconds. How fast is the bus now going?

A motorcycle starting at rest accelerates at 8 m/s^2 for 4 seconds. How fast is the motorcycle now going?

A car goes from 40 m/s to 20 m/s in 2 seconds. What is the acceleration of the car?

A rocket accelerates at 20 m/s^2 and goes from zero to 200 m/s. How long did the rocket accelerate?

Newton’s Third Law

Newton’s Third Law

Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first object.

1. Identifying Action and Reaction Forces. Draw a picture and describe the pair of forces.

Car crashing into a wall
Person pushing another person
Gun shooting a bullet
Mass falling to earth
Mass hitting the earth
Helicopter
Rocket

2. Acceleration is not the same unless masses are the same.

Lab: Use the tracks and two carts to create an action/reaction pair by triggering the spring mechanism between them.

1. Describe what happens to each cart in terms of the Third Law.

2. Add a weight to one of the carts and repeat the experiment. What happens now? Is the third law still supported by what happened? Why or why not? How is the Second Law involved in what happened?

3. Add another weight (2 total) to the cart you added one to in step 2. What happens now?

For all the steps above, was Newton’s third law verified? How does Newton’s Second Law explain what happened in each case?

Homework: Identify 3 pairs of action/reaction forces during your day. Write down what is happening, draw a picture, and identify the forces.