Kinetic Energy and Work Summary Page

Definition of the Joule

1 J = 1 N $\cdot$ m = 1 kg$\cdot$ m2/s2

Work done by an external force

W =F dx

Work done by a force over a distance

W = . = ||·||·cos$\theta$= (F$\cdot$ cos$\theta$)$\cdot$ d = F$\cdot$ d$\cdot$ cos$\theta$

Force exerted by a spring

= -k $\Delta$ = -k ( - o)

Work done in compressing or extending a spring

W = kx2

Kinetic energy of an object

K = mv2

The work-energy theorem

W = $\Delta$K

Potential energy of a spring

Uspring = (1/2)kx2

Gravitational potential energy

Ugravity = mgh

Conservation of total energy

E= mv2 + U = mvo2 + Uo

Average power

Pav = $\Delta$W/$\Delta$t = W/t

Power exerted by a force

Pav = (·)/t = ·

Efficiency

$\epsilon$ = Wout/Ein = Pout/Pin