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[[ for questions 2 and 4 the image is attached ]]
1. In which one of the following situations is zero net work done?
(a) A ball rolls down an inclined plane.
(b) A physics student stretches a spring.
(c) A projectile falls toward the surface of Earth.
(d) A box is pulled across a rough floor at constant velocity.
(e) A child pulls a wagon across a rough surface causing it to accelerate.
2. A concrete block is pulled 7.0 m across a frictionless surface by means of a rope. The tension in the rope is 40 N; and the
net work done on the block is 247 J. What angle does the rope make with the horizontal?
(a) 28° (b) 41° (c) 47° (d) 62° (e) 88°
3. Mike is cutting the grass using a human-powered lawn mower. He pushes the mower with a force of
45 N directed at an angle of 41° below the horizontal direction. Calculate the work that Mike does on
the mower in pushing it 9.1 m across the yard.
(a) 510 J (b) 460 J (c) 410 J (d) 360 J (e) 310 J
4. A constant force of 25 N is applied as shown to a block which undergoes a displacement of 7.5 m to the right along a frictionless surface while the force acts. What is the work done by the force?
(a) zero joules (b) +94 J (c) −94 J (d) +162 J (e) −162 J
5. Which one of the following statements concerning kinetic energy is true?
(a) It can be measured in watts.
(b) It is always equal to the potential energy.
(c) It is always positive.
(d) It is a quantitative measure of inertia.
(e) It is directly proportional to velocity.
6. The kinetic energy of a car is 8 × 106 J as it travels along a horizontal road. How much work is required to stop the car in 10 s?
(a) zero joules (b) 8 × 104 J (c) 8 × 105 J (d) 8 × 106 J (e) 8 × 107 J
7. How much energy is dissipated in braking a 1000-kg car to a stop from an initial speed of 20 m/s?
(a) 20 000 J (b) 200 000 J (c) 400 000 J (d) 800 000 J (e) 10 000 J
8. The kinetic energy of an 1100-kg truck is 4.6 × 105 J. What is the speed of the truck?
(a) 21 m/s (b) 29 m/s (c) 33 m/s (d) 17 m/s (e) 25 m/s
9. A 40-kg block is lifted vertically 20 meters from the surface of the earth. To one significant figure, what is the change in the gravitational potential energy of the block?
(a) +800 J (b) −800 J (c) +8000 J (d) −8000 J (e) zero joules
10. The kinetic energy of a car is 8 × 106 J as it travels along a horizontal road. How much power is required to stop the car in 10 s?
(a) zero watts (b) 8 × 104 W (c) 8 × 105 W (d) 8 × 106 W (e) 8 × 107 W
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