4.1 Work and Machines

The amount of work done depends on the

• amount of force applied

• mass and distance the object moves

• mass and speed with which the object moves

• amount of force and distance the object moves.

If no force is applied on a body its velocity remains the same but its kinetic energy keeps changing

• TRUE

• FALSE

Assume that a friend hands you a heavy book to hold as he turns the combination lock on his locker. Which of you does more work?

• you

• your friend

• you both do the same amount of work

Work is done when a body moves through a certain distance in the direction of application of force

• True

• False

Energy transfer takes place during the process of work.

• TRUE

• FALSE

Choose the ways that machines may change a force.

• increasing the force

• increasing speed

• changing the direction of the force

• All of the above

If a machine requires an input of 5,000 joules of work to put out 4,000 joules of work, what is the machine’s efficiency?

• 80%

• 100%

• 40%

• 60%

If Omar pushes a crate weighing 60 N up a ramp and the MA for the ramp is 2, then the force applied by Jane is at least _____.

• 45N

• 30 N

• 120N

• 25N

What is the equation for calculating work when force and distance are known?

• work = force /distance

• work = force+distance

• work = force×distance

• work = distance/force

An example of a machine that increases the force is

• Bicycle

• Skate Board

• Car Jack

• Fixed Pulley