Work, Energy, and Power

A freshman stands on his toes and lifts a World Civilization book to the top shelf of his locker.

+

At Great America, a roller coaster car is lifted to the peak of the first hill on the Shock Wave.

+

A catcher puts out his mitt and catches the baseball

-

A falling parachutist opens the chute and slows down.

-

An eastward-moving car skids to a stop across dry pavement.

-

A toy car is moving along with 0.40 joules of kinetic energy. If its speed is doubled, then its new kinetic energy will be

1.60 J

A young boy's glider is soaring through the air, possessing 0.80 joules of potential energy. If its speed is doubled and its height is doubled, then the new potential energy will be

1.60 J

internal forces

Fgrav Fspring

External Forces

Fnorm Ffrict Fair Fapp Ftens

Which would ALWAYS be true of an object possessing a kinetic energy of 0 joules?

It is at rest.

Which would ALWAYS be true of an object possessing a potential energy of 0 joules?

It is on the ground.

Which sets of units represent legitimate units for the quantity work?

Joule N x m Foot x pound kg x m2/sec2

If an object is at rest, it certainly does NOT possess this form of energy. Depends upon object mass and object speed.

KE

The total mechanical energy of an object is the

KE plus the PE of the object at any instant during its motion

Depends upon object mass and object height

PE

An impulse is a force acting over some amount of time to cause a change in momentum. On the other hand, work is a ________ acting over some amount of _______ to cause a change in ________

force, distance, energy

What's another way to find force?

m*g

Work is a ______________; a + or - sign on a work value indicates information about _______.

scalar, whether the work adds or removes energy from the object

If an object moves in such a manner as to conserve its total mechanical energy, then

the sum of the kinetic energy and the potential energy remains the same throughout its motion