Sample Work, Energy, and Simple Machines Problems for extra practice

A boy lifts a 600 Newton rock 8cm into the air using a lever.  He pushes on the lever 100 N.

If the lever is an Ideal machine, what distance does he push the lever?

He finds that it is not ideal and he really needs to push the lever 52 cm, to lift the rock.

What is the IMA, MA, and efficiency of this lever?  Where does the extra energy go?

How much work does he do?  How much work is actually done (work output)?

Rockin dude pulls on a simple pulley and lifts a 400 kg crate up in the air 2 meters.

If this simple machine is 90% efficient, and he pulls in 8 meters of rope

• How much work does he put into the machine?
• How much work does he get out of the machine?
• What is the MA and IMA of the machine?

**Try the rest after we have talked about power

He does this in 30 seconds. How much power does he have to put into the machine?

How much power does he develop while doing this task? (get out of the machine)

Where does the extra energy go?

A boy pulls a 200 Newton crate horizontally with a force of 50 Newtons.  He pulls on a rope that makes a 30 degree angle with the horizontal.  He pulls the crate 12 meters.

How much work does he do?

If he were to do this in 10 seconds, how much power would he develop?

A satellite with a force of gravity on it of 25,000 Netwons, travels around a near circular path around the earth.  The radius of the orbital period is 6.4x105 meters.

If the satellite travels at a nearly constant speed, how much work is done by gravity?  (see page 226)