Physics test study - Unit 3 - Work, Energy, Power

Kinetic energy (definition, equation)

Kinetic: referring to motion

Energy: the ability to do work (work is the change in KE)

K = (1/2)mv²

Can kinetic energy be negative?

NO

Kinetic energy is a SCALAR quantity, with no direction, so it is always positive

Work (definition, equation)

> The energy transferred when a force acts on an object and causes it to move a certain distance

W = Fd

W = the change in KE = (1/2)mvf²-(1/2)mvi²

Can work be negative?

Yes

• Work is neg (-) when force is applied in the OPPOSITE direction as motion

• Work is pos (+) when force is applied in the SAME direction as motion

When does work cause an increase in energy in a system?

• When work is positive (+), the system gains energy.

• When work is negative (-), the system loses energy.

What is a joule?

Unit used for

• work

• K energy

• U energy

and is = to 1 N acting upon 1 m

Work- Energy Theorem

the total work done by the sum of all forces on a particle equals the change in its kinetic energy:

Wnet=ΔKE

• If positive(+) net work is done on an object, its kinetic energy increases (it speeds up).

• If negative(-) net work is done, its kinetic energy decreases (it slows down).

Power (definition, equation)

The rate at which work is done, or energy is transferred

Pinst= W/Δt = ΔE/Δt

Pavg= Fv

What unit is used for power in AP Physics I?

Watts (W)

1 Joule(J) / second(s)

How do you find work in a graph?

Work = Fd

W = the area under a Force vs Displacement graph

Potential energy (definition, equations)

Stored energy an object possesses due to its position.

• the amount of potential energy an object has is equal to the work done to give that object that energy (usually through moving it to some location)

ΔUgravitational=mgΔy

Uspring=(1/2)kΔx²