(Savvas 14.2) Ch.14.2 Work and Machines

Is the following sentence true or false? A machine can make work easier to do by changing the size of the force needed, the direction of a force, or the distance over which a force acts.

• True

• False

Give an example of a machine that changes the direction of an applied force.

• Pulley

• Wheel and axle

Tags

NGSS.MS-PS2-1

NGSS.MS-PS2-2

When you make several trips to unload a few heavy items from a car instead of moving them all at once, the total distance over which you exert yourself ________.

• increases

• decreases

• remains the same

• doubles

The output force of a machine (i.e. water moved by an oar) (work output) is always less than the force that was put into the machine (i.e. muscles pulling on the oar) (work input) because of ________.

• friction or energy losses

• increased power

• reduced efficiency

• mechanical advantage

Circle the letter of the definition for input force.

• the amount of force exerted by a machine

• the amount of friction slowing the speed of a machine

• the amount of work done by a machine

• the amount of force exerted on a machine

Write a word equation that describes work input.

• Work input = Force x Distance

• Work input = Mass x Acceleration

• Work input = Power x Time

• Work input = Energy x Time

Is the following sentence true or false? Every machine uses some of its work input to overcome friction.

• True

• False

The force exerted by a machine is called the _________ force.

• output

• input

• mechanical

• applied

Choose the letter of the expression that equals the work output of a machine.

• Input distance / Output distance

• Output distance × Input distance

• Output distance / friction

• Output distance × Output force

Is the following sentence true or false? Output work always is less than input work.

• True

• False

Tags

NGSS.MS-PS3-5