PS chapter 12

If a person tries to lift a heavy box for 5 seconds and cant make it budge, the work done on the box is LESS THAN 0.

• TRUE

• FALSE-equal to

Machines DECREASE the amount of energy that is needed to do work.

• TRUE

• FALSE-increase

Because of friction, using machines INCREASES the amount of energy that is need to do work

• TRUE

• FALSE

An arrangement of multiple pulleys causes the direction of the output force to be OPPOSITE to the direction of the input force.

• TRUE

• FALSE-same as

What are the units of work

• J

• NxM

• kgxm2/s2

• all of the above

Which of the following processes requires the most work?

• A 10 kg weight rests on a table

• A person holds a 1 kg weight still with outstretched arms.

• A person lifts a 1 kg weight 1 m off the floor

• A 10 kg ball is rolled across the floor at a constant speed for a distance of 10 m

What are the units of power?

• watts

• horsepower

• joules per second

• all of the above

A machine is a device that

• requires less work to do a given task

• decreases the amount of work done by a given force

• increases energy

• can multiply and change the direction of an input force

A 1st class lever has the

• fulcrum at one end and the output force between the fulcrum and the input force

• fulcrum at one end and the input force between the fulcrum and the output force

• fulcrum is in the middle

• input force in the middle

Which of the following is an example of a wheel and axle

• a block and tackle

• a pulley

• a screwdriver

• a nutcracker