1. An adult generates 72 W of power as she pulls a sled forward across a flat snowy surface with a force of 80 N. The adult pulls with this force for 4.5 minutes. What distance does the sled move?
180 m
130 m
240 m
280 m
2. An apartment dweller runs a 120-W stereo system for 16 hours a month, on average. The landlord reduces the cost of electricity by 0.37 cents/kWh. How much money will the apartment dweller save per year?
2.4 cents
32 cents
8.5 cents
0.71 cent
3. The graph shows the relationship between a force acting on an object and the displacement of the object. To which situation does the graph best apply?
a car accelerating at a constant rate along a flat highway
a car traveling at a constant speed along a flat highway
a rock tossed at an angle off the roof of a tall building
a spaceship increasing its rate of acceleration through space
4. A model rocket with a mass of 0.212 kg is launched into the air with an initial speed of 84 m/s. How much kinetic energy will the rocket have at a height of 214 m? Assume there is no wind resistance.
303 J
747 J
634 J
444 J
5. A spring is compressed to a displacement of -3.9 m from equilibrium. Then the spring is released and allowed to stretch to a displacement of -1.5 m from equilibrium. The spring constant is 11 N/m. What best describes the work involved as the spring stretches?
The spring performs 140 J of work
140 J of work is performed on the spring.
71 J of work is performed on the spring.
The spring performs 71 J of work.
6. A student releases a rock of mass m from a height h above the ground. Values for which set of variables are essential to calculate the speed at which the rock strikes the ground? Assume that the acceleration due to gravity (g) is known, and that the effect of air resistance and other nonconservative forces are negligibly small.
m, but not h
neither h nor m
h and m
h, but not m