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9.1 Work, Power, and the Work–Energy Theorem

14 .
A baseball player exerts a force of 100 N on a ball for a distance of 0.5 m as he throws it. If the ball has a mass of 0.15 kg , what is its velocity as it leaves his hand?
  1. 36.5 m/s
  2. 25.8 m/s
  3. 25.8 m/s
  4. 36.5 m/s

A boy pushes his little sister on a sled. The sled accelerates from 0 to 3.2 m/s . If the combined mass of his sister and the sled is 40.0 kg and 18 W of power were generated, how long did the boy push the sled?

  1. 205 s
  2. 128 s
  3. 23 s
  4. 11 s

9.2 Mechanical Energy and Conservation of Energy

16 .
What is the kinetic energy of a 0.01 kg bullet traveling at a velocity of 700 m/s ?
  1. 3.5 J
  2. 7 J
  3. 2.45 × 10 3 J
  4. 2.45 × 10 5 J
17 .
A marble is rolling across a flat surface with a velocity of 2 m/s. It begins to roll up a ramp. Ignoring rotational kinetic energy and friction, what will be the vertical height of the marble when it comes to a stop before rolling back down?
  1. 0.1 m
  2. 0.2 m
  3. 0.4 m
  4. 2 m

The potential energy stored in a compressed spring is U= 1 2 k x 2 U= 1 2 k x 2 , where k is the force constant and x is the distance the spring is compressed from the equilibrium position. Four experimental setups described below can be used to determine the force constant of a spring. Which one(s) require measurement of the fewest number of variables to determine k? Assume the acceleration due to gravity is known.

  1. An object is propelled vertically by a compressed spring.
  2. An object is propelled horizontally on a frictionless surface by a compressed spring.
  3. An object is statically suspended from a spring.
  4. An object suspended from a spring is set into oscillatory motion.
  1. I only
  2. III only
  3. I and II only
  4. III and IV only

9.3 Simple Machines


A man is using a wedge to split a block of wood by hitting the wedge with a hammer. This drives the wedge into the wood creating a crack in the wood. When he hits the wedge with a force of 400 N it travels 4 cm into the wood. This caused the wedge to exert a force of 1,400 N sideways increasing the width of the crack by 1 cm . What is the efficiency of the wedge?

  1. 0.875 percent
  2. 0.14
  3. 0.751
  4. 87.5 percent

An electrician grips the handles of a wire cutter, like the one shown, 10 cm from the pivot and places a wire between the jaws 2 cm from the pivot. If the cutter blades are 2 cm wide and 0.3 cm thick, what is the overall IMA of this complex machine?

The image is a picture of wire cutters with red handles. The pinchers are closed.
  1. 1.34
  2. 1.53
  3. 33.3
  4. 33.5
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