PHYS 250 Exam 4 Test Questions with
Complete Solutions.
A machine uses 500 J of electric energy to raise a heavy mass, increasing its potential energy by
400 J. What is the efficiency of this process?
a. 20%
b. 600 J
c. 80%
d. 100 J
e. -68 J - Answer c
A truck has eight times the mass of a car and is moving at half of the speed of the car. If Kt and
Kc refer to the kinetic energies of truck and car respectively, it is correct to say that
a. Kt = 2Kc.
b. Kt = 16Kc.
c. Kt = 4Kc.
d. Kt = Kc.
e. Kt = Kc. - Answer a
You slam on the brakes of your car in a panic, and skid a certain distance on a straight level road.
If you had been traveling twice as fast, what distance would the car have skidded, under the
same conditions?
a. It would have skidded 4 times farther.
b. It is impossible to tell from the information given.
c. It would have skidded 1.4 times farther.
d. It would have skidded twice as far.
e. It would have skidded one half as far. - Answer a
The graphs below show the magnitude F of the force exerted by a spring as a function of the
displacement x the spring has been stretched. For which one of the graphs does the spring obey
Hooke's law?
A- horizontal line
B- linear increase
C- increasing curve up
D- negative curve up
E- decreasing curve up - Answer b
Complete Solutions.
A machine uses 500 J of electric energy to raise a heavy mass, increasing its potential energy by
400 J. What is the efficiency of this process?
a. 20%
b. 600 J
c. 80%
d. 100 J
e. -68 J - Answer c
A truck has eight times the mass of a car and is moving at half of the speed of the car. If Kt and
Kc refer to the kinetic energies of truck and car respectively, it is correct to say that
a. Kt = 2Kc.
b. Kt = 16Kc.
c. Kt = 4Kc.
d. Kt = Kc.
e. Kt = Kc. - Answer a
You slam on the brakes of your car in a panic, and skid a certain distance on a straight level road.
If you had been traveling twice as fast, what distance would the car have skidded, under the
same conditions?
a. It would have skidded 4 times farther.
b. It is impossible to tell from the information given.
c. It would have skidded 1.4 times farther.
d. It would have skidded twice as far.
e. It would have skidded one half as far. - Answer a
The graphs below show the magnitude F of the force exerted by a spring as a function of the
displacement x the spring has been stretched. For which one of the graphs does the spring obey
Hooke's law?
A- horizontal line
B- linear increase
C- increasing curve up
D- negative curve up
E- decreasing curve up - Answer b
