Practice Exam 2.1

Problem 1

A 200 g ball is dropped from a height of 2.0 m and reaches a speed of 6.3 m/s, and then bounces on a hard floor.

  1. Draw an impulse-momentum bar diagram for the situation.
  2. What is the average force applied to the ball?
  3. How fast is the ball moving after bouncing from the floor? (Answer: 500 N, 3.8 m/s)

Problem 2

A cart with mass 340 gmoving on a frictionless linear airtrack at an initial speed of 1.2 m/s

undergoes an elastic collision withan initially stationary cart of unknownmass. After the collision, the first cart continues in its originaldirection at 0.66 m/s while the second moves at 1.9 m/s.

  1. Draw a momentum bar diagram for this situation.
  2. What is the mass of the second cart? (Answer: 0.099 kg)

Problem 3

A single frictionless roller-coaster car of mass 825 kg tops the first hill with speed 17.0 m/s at height 42.0 m.

  1. Draw an energy bar diagram from point A to point B. What is the speed of the car at point B?
  2. How high will the car go on the last hill, which is too high for it to cross? (Answer: 26.5 m/s, 56.7 m)

Problem 4

How many slices of pizza must you eat to walk for 1.0 h at a speed of 5.0 km/h (= 3.1 mph)? (Assume your mass is 68 kg.) Assume a slice of pizza is 300 Cal.

(Answer: ≈ 4 slices)

Problem 5

Use short concise sentences to answer the following questions using physics principles. Make sure to explain your reasoning for each answer

a.Why, when you release an inflated, untied balloon, does it fly across the room?

b.Why is it tiring to push hard against a solid wall even though no work is done?

c.A woman bounces on a trampoline, going a little higher with each bounce. Explain how she increases the total energy.

d.According to the table of Problem 4, cycling at 15 km/h requires less metabolic energy than running at15 km/h. Suggest reasons why thisis the case.