A watt is equal to
a. 746 horsepower.
b. one calorie.
c. one joule.
d. 1 J/s.
e. a unit of energy.
[Ques. 2] About how many 100-W light bulbs would you have to light up to use energy at the rate of one horsepower?
a. one or two
b. seven or eight
c. the question doesn't make sensehp and W are unrelated
d. dozens
e. none of the above
[Ques. 3] After an elastic collision of two balls, the kinetic energies of the two balls are measured to be 12 J and 24 J. What can be said about the kinetic energy of the two balls before the collision?
a. nothingnot enough information is given
b. the balls had the same energies, 12 J and 24 J, respectively
c. the total kinetic energy of the two balls was 36 J
d. none of the above
[Ques. 4] A person runs up a long flight of stairs in 10 seconds. If the person's weight is 600 N and the vertical height of the stairs is 20 meters, the person's power output is
a. 0.
b. 3 W.
c. 30 W.
d. 1,200 W.
e. 12,000 W.
[Ques. 5] A 2-kg car moving towards the right at 4 m/s collides head on with an 8 kg car moving towards the left at 2 m/s, and they stick together. After the collision, the velocity of the combined bodies is
a. 0.
b. 0.8 m/s towards the right.
c. 0.8 m/s towards the left.
d. 2.4 m/s towards the right.
e. 2.4 m/s towards the left.
[Ques. 6] Which of the following quantities are conserved in an isolated system?
a. mass b. energy
c. momentum d. all of the above
[Ques. 7] Using a lever to move a rock reduces the force a person must exert. What does it do to the work the person must do?
a. it reduces the work also b. the work stays the same
c. the work increases d. none of the above
[Ques. 8] When we say work is done against a force, we mean the force does
a. none of the work. b. positive work.
c. negative work. d. zero work.
[Ques. 9] When we say work is done by a force, we mean the force does
a. all the work. b. positive work.
c. negative work. d. zero work.
[Ques. 10] Consider a situation where a constant force of 25 N acts on an object having a mass of 2 kg for 3 seconds.What is the magnitude of the change in the object's momentum?
a. 150 kg m/s
b. 50 kg m/s
c. 75 kg m/s
d. undeterminednot enough information given
e. none of the above
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