A 62.0-kg woman runs up a flight of stairs having a rise of 4.28 m in a time of 4.20 s. What average power did she supply?
a. 63.2 W
b. 619 W
c. 596 W
d. 629 W
e. 609 W
[Ques. 2] A 180-hp engine can deliver, in SI units, an average power of ____. (1 hp = 746 W)
a. 2.4E1 W
b. 4.1E+3 W
c. 1.3E+5 W
d. 1.8E+2 W
e. 9.3E+2 W
[Ques. 3] The unit of power, watt, is dimensionally the same as:
a. joule-second.
b. joule/second.
c. joule-meter.
d. joule/meter.
[Ques. 4] The rate at which work is done is equivalent to which of the following?
a. increase in potential energy
b. thermal energy
c. potential energy
d. power
[Ques. 5] The quantity of work equal to one joule is also equivalent to which of the following?
a. watt
b. watt /s
c. watt / s
d. watt /s2
[Ques. 6] In 1908 there was a huge explosion referred to as the Tunguska event which occurred in Siberia. Apparently this was caused by a very large meteorite, a small asteroid, or a comet colliding with the Earth. If the energy released, estimated at 5 1016 J, were from the kinetic energy of the object, what would have been its approximate mass if its speed had been 104 m/s?
a. 106 kg b. 109 kg
c. 1012 kg d. 1014 kg
[Ques. 7] A block is projected with speed v across a horizontal surface and slides to a stop due to friction. The same block is then projected with the same speed v up an incline where is slides to a stop due to friction. In which case did the total mechanical energy of the block decrease the least?
a. This problem cannot be solved since it was not indicated whether the horizontal surface and the incline both had the same coefficient of kinetic friction.
b. The case on the horizontal surface had the least decrease in total mechanical energy.
c. The case on the inclined surface had the least decrease in total mechanical energy.
d. In both cases the decrease in mechanical energy was the same.
[Ques. 8] In a problem using energy considerations to solve for the speed of a ball thrown from the top of a building when it strikes the ground below, where should the potential energy have its zero value?
a. It should be at the level from where the ball is thrown.
b. It should be at the ground level where the ball hits.
c. It should be slightly below ground level so the potential energy is always positive.
d. It doesn't matter since only differences in potential energy matter in solutions.
[Ques. 9] Three different-mass projectiles are launched from the top of a building each at different angles of elevation. Each particle has the same initial kinetic energy. Which particle has the greatest kinetic energy just as it impacts with the ground?
a. The one launched at the highest angle of elevation.
b. The one with the highest mass.
c. The one with the lowest mass.
d. They all will have the same kinetic energy on impact.
[Ques. 10] A Hooke's law spring is compressed a distance d and is used to launch a particle of mass m vertically to a height h above its starting position. Under double the compression, the spring is now used to launch a particle of mass 2m. How high does the second mass rise above its starting position?
a. h
b. 2h
c. 3h
d. 4h
Quick Reply
