How much does the energy change?

If the velocity of an object is changed by one fourth, how much does momentum change?

How Much does the energy change?

What is the relationship between Impulse and momentum?

Is it correct to say impulse is equal to momentum? Explain.

Is it correct to say work is equal to kinetic energy? Explain.

Given the two graphs below of Impulse and velocity, which one shows a larger mass? Explain why!

2. A 1000-kg car strikes a tree at 30 km/h (convert to m/s) and comes to a stop in .15 seconds. Find its initial momentum, and the average force in pounds on the car while it is being stopped. (p = 8333 or 8,300 kgm/s; F = 55553 or 56,000 N = 12,000 pounds).

Find its kinetic energy. (34722 J)

Find the impact distance. (.63 m)

Find the acceleration of the car. (55.5 or 56 m/s^2)

Use the correct kinematic equation to show you get the same distance you just found.

Water emerging from a hose at a rate of 3.0 L/s and a speed of 8.0 m/s strikes a person. If the water loses all its momentum on impact, find the force on the person in pounds over a period of two second. The mass of one liter of water is one kilogram. (F = 48 N = 11 pounds)

3. A truck is driving down the road and comes to a stop at a stoplight. Explain how it would be possible for a bike to actually require more of a stopping force.

Is it possible for an object to have more kinetic energy but less momentum than another object? Explain why or why not.

How about less kinetic energy but more momentum? Explain why or why not.

4. A 150-g baseball reaches a batter with a speed of 25 m/s. After it has been struck, it flies off the bat at 30 m/s in the opposite direction. If the impact time was 1.0 milliseconds, find the force exerted by the bat. (F = -8250 N = 1855 pounds).

A 4.0-kg bird (flying at 5.0 m/s) flies right into the windshield of an airplane flying in the opposite direction. If the impact lasted .001 seconds, and the force on the windshield was 740,000 N, find the velocity of the airplane. ( V = +180 m/s)

The same bird flies into a truck windshield (He didn't learn from the first time), where the truck is traveling at 25 m/s. If the impact time was 1.0 miliseconds, and the impact force was 124,000 Newtons, find the initial speed of the bird. (V = 6.0 m/s)

There is a 50-kg man running at 6 m/s. How fast must a 75-kg man run so that he has the same momentum? ( V = 4 m/s)

With what force would they hit if both men were to run into a door, and the impact lasted .10 seconds. (F = 3000 N)

How much work was done on the 50-kg man to bring him to a stop? (900 J)

How much work was done on the 75-kg mas to bring him to a stop? (600 J)

Which man sustained the most damage and why?

Find the impact distance of the 50-kg man. (.30 meters)

Find the impact distance of the 75-kg man. (.20 meters)

Interpret the last two answers. In other words, explain what that distance means in terms of the door during impact, if say the door were open and was able to move on its hinges. Use the diagram below to illustrate your answer.

(The doors' hinges are at the point where they meet the horizontal line. Draw the position of the door after impact.)

5. Define Newton's Third Law of Motion:

What is the one difference between the first two Laws and the Third Law?

Explain using Newton's Third Law the following situation: A person is sitting in a row boat and is holding onto another row boat, which is next to his boat. He pushes the boat away, and he goes backwards.

Why do the two forces in the previous question not cancel, which would mean neither boat would move?

Why would a person naturally think a semi-truck hit a compact car with the greater force in a head-on collision?

How can you explain to someone that they actually hit each other with equal and opposite forces?

We have been using Impulse and and work to find starting and stopping forces on objects. Explain why it hurts when you supply a force with your hand to stop a baseball:

Reflect on the following statement: "You cannot touch someone without them touching you." The context of this statement is referring to touching someone's life, or making a difference. Do you think it is impossible to make a difference in a person' life without it affecting your own? Explain.

6. What does it mean to say a quantity is conserved in physics?

What are the two conservation laws learned thus far in class?

Listed below are the three types of collisions. Match them to the correct statement:

A. Elastic Collision

B. Inelastic Collision

C. Completely Inelastic Collision

  There is some deformation between the two objects, which means some of the kinetic energy is lost due to the work done in the form of heat; thus, energy is not conserved within the system. Momentum is conserved.

  There is no deformation between the objects, which means there is no loss of energy; thus, energy is conserved within the system. Momentum is conserved.

  There is maximum energy loss due to the work done in the form of heat, and the objects generally stick together after the collision; thus, energy is not conserved within the system. Momentum is conserved.

A billiards ball with a mass of 2.0-kg collides with a cue ball (at rest) with a mass of 1.5-kg with a velocity of 3.5 m/s. Find v1' and v2' and show that momentum and energy are both conserved. Assume an elastic collision. (V1'= .50 m/s; V2'= 4.0 m/s; Initial and Final Mom. = 7.0 kgm/s; Initial and Final Energy = 12.25 J)

Draw in the direction of the balls after the collision:

Finding V1' and V2':

  Momentum Conservation:

  Energy Conservation:

  A billiards ball with a mass of 2.0-kg collides with another billiards ball (at rest) with the same mass and with a velocity of 3.5 m/s. Find v1' and v2' and show that momentum and energy are both conserved. Assume an elastic collision. (V1'= 0 m/s; V2'= 3.5 m/s; Initial and Final Mom. = 7.0 kgm/s; Initial and Final Energy = 12.25 J)

Draw in the direction of the balls after the collision:

Finding V1' and V2':

  Momentum Conservation:

  Energy Conservation:

  a cue ball with a mass of 1.5-kg collides with another billiards ball (at rest) with a mass of 2.0-kg with a velocity of 3.5 m/s. Find v1' and v2' and show that momentum and energy are both conserved. Assume an elastic collision. (V1'= -.50 m/s; V2'= 3.0 m/s; Initial and Final Mom. = 7.0 kgm/s; Initial and Final Energy = 9.19 J)

Draw in the direction of the balls after the collision:

Finding V1' and V2':

  Momentum Conservation:

  Energy Conservation:

Why is there only one outcome to any type of collision? Explain.

7. A car with a mass of 500.0-kg collides with another car at rest that has a mass of 400.0-kg. If the car was traveling 45.0 mph and the completely inelastic collision occurred on an icy road, find the final speed of the two cars together. (V' = 25 mph)

If a car traveling at 20 m/s collides with another car at rest (completely inelastic) and their final velocity together is 10 m/s, what can you conlude about their masses?

If a car traveling at 20 m/s collides with another car at rest (completely inelastic) and their final velocity together is 15 m/s, what can you conlude about their masses?

If a car traveling at 20 m/s collides with another car at rest (completely inelastic) and their final velocity together is 5 m/s, what can you conlude about their masses?

Explain why to the last three questions:

You and a friend are playing on an icy pond. You pull your friend with a rope, and your friend moves towards you with a velocity of + 1.5 m/s. Find your velocity if your mass is 60.0-kg and your friends mass is 80.0-kg. (V2' = - 2.0 m/s)

You then play with another friend on the same icy pond and pull her with a rope, and she moves towards you with a velocity of + 2.0 m/s, and you move towards her with a velocity of - 1.5 m/s. Find the mass of your friend. (45 kg)

You and a friend are floating in outer space. Your mass is 80.0-kg and your friend's mass is 100.0-kg. If you pushed your friend and you went backwards with a velocity of - 5.0 m/s, find the velocity your friend will have. (V2' = + 4.0 m/s)

Why is your speed larger than your friend's speed? Explain using both Newton's Third Law and Momentum Conservation:

What would happen to your speed as the masses of the two people get closer to the same?

If someone were to ask you why Newton's Apparatus works the way it does, what would you say?

For Honors Physics Only:

You and a friend are playing catch in space. If you, with a mass of 55-kg, throw a ball with a mass of 5-kg, and your friend with a mass of 45-kg catches it and travels backwards with a speed of .60 m/s, find how fast you are traveling backwards. (V2' = - .545 m/s)