PLC Activity #12

Practice Exam 2.1

All problems are worth 20 points

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/sundergoes 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

A compressed-air cylinder is known to fail if the pressure exceeds 110 atm. A cylinder that was filled with 1000.0 moles of air to 26× 105 Pa at 30°C is stored in a warehouse. Unfortunately, the warehouse catches fire and the temperature reaches 950°C.

a.What is the container's volume?

b.Does the cylinder explode?(Answer: 0.97 m3, 105×105 Pa)

Problem 5

At one point in a pipeline (diameter of 1 cm) the water's speed is 3.00 m/s and the gauge pressure is 50.0 kPa. Find the gauge pressure at the second point (diameter of 2 cm) in the line, 11.0 m lower than the first, if the pipe diameter at the second point is twice that at the first.Hint: calculate the speed of the water at the second point first. (ρwater= 1000 kg/m3)

(Answer: 162kPa)

Problem 6

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.Why does food cook faster in a pressure cooker than in an open pot of boiling water?

e. During the Great Mississippi flood of 1993, the levees in St. Louis rupture. What location would you expect them to rupture first? Why?