Work and Energy

[Jessica]

Work is done when a force causes displacement in the direction of that force; it is the product of the force/displacement and the component of displacement/force in the direction of that force. When done on an object, the object is given energy. Having energy means having the ability to do work.

W = F[sub]x[/sub]Δx or F[sub]y[/sub]Δy

the force and displacement must be parallel

It is a SCALAR quantity

While work can be negative, the negative sign does not refer to direction. Rather, the negative work indicates that energy was lost. Positive work indicates an energy gain.

[Jessica]

A constant force F that moves an object a distance s in the same direction as the force does a work
W = Fs

[Jessica]

A object of mass m moving with speed v has a kinetic energy defined as the quantity


SI unit: Joules (J)



Work-Energy Theorem

A work done by the net force acting on an object is equal to the change in its kinetic energy.

W = ΔK = K[sub]f[/sub] − K[sub]0[/sub] = ½mv[sub]f[/sub]² − ½mv[sub]0[/sub]²