Physical Science Chapter 12 Practice Test Name______

Modified True/False

Indicate whether the sentence or statement is true or false. If false, change the identified word or phrase to make the sentence or statement true.

____1.If a person tries to lift a heavy box for 5 seconds and can’t make it budge, the work done on the box is less than zero. ______

____2.Machines decrease the amount of energy that is needed to do work. ______

____3.Because of friction, using machines increases the amount of energy that is needed to do work ______

____4.An arrangement of multiple pulleys causes the direction of the output force to be opposite to the direction of the input force. ______

Multiple Choice

Identify the letter of the choice that best completes the statement or answers the question.

____5.What are the units of work?

a. / J / c. / kgm2/s2
b. / Nm / d. / All of the above

____6.Which of the following processes requires the most work?

a. / A 10 kg weight rests on a table.
b. / A person holds a 1 kg weight still with outstretched arms.
c. / A person lifts a 1 kg weight 1 m off the floor.
d. / A 10 kg ball is rolled across the floor at a constant speed for a distance of 10 m.

____7.What are the units of power?

a. / watts / c. / joules per second
b. / horsepower / d. / All of the above

____8.A machine is a device that

a. / requires less work to do a given task.
b. / decreases the amount of work done by a given force.
c. / increases energy.
d. / can multiply and change the direction of an input force.

____9.A first-class lever has the

a. / fulcrum at one end and the output force between the fulcrum and the input force.
b. / fulcrum at one end and the input force between the fulcrum and the output force.
c. / fulcrum in the middle.
d. / input force in the middle.

____10.A wheelbarrow is an example of a

a. / first-class lever. / c. / third-class lever.
b. / second-class lever. / d. / fourth-class lever.

____11.Which of the following is an example of a wheel and axle?

a. / a block and tackle / c. / a screwdriver
b. / a pulley / d. / a nutcracker

____12.Which of the following is not in the inclined plane family?

a. / a wedge / c. / a ramp
b. / a screw / d. / a wheel and axle

____13.Which of the following statements about work and energy is not true?

a. / When work is done, energy is transferred or transformed.
b. / Energy may be defined as the ability to do work.
c. / Work and energy are always equal.
d. / Work and energy have the same units.

____14.What is the gravitational potential energy of a 55 kg box that is 8.0 m above the ground?

a. / 5500 J / c. / 4300 J
b. / 3400 J / d. / 550 J

____15.Gravitational potential energy depends on the

a. / the mass of the object. / c. / the acceleration due to gravity.
b. / the height of the object. / d. / All of the above

____16.The brakes on a car exert a frictional force of 6000 N in getting the car to stop. If the work done by the brakes is 120 000 J in coming to a stop, how many meters did the car travel after the driver applied the brakes?

a. / 6 m / c. / 12 m
b. / 20 m / d. / 40 m

____17.The law of conservation of energy states that

a. / the energy of a system can disappear.
b. / it is impossible to make a perpetual motion machine.
c. / energy cannot change form.
d. / energy can neither be created nor destroyed.