POTENTIAL ENERGY AND CONSERVATION OF ENERGY
CONSERVATIVE AND NONCONSERVATIVE FORCE
CONSERVATIVE
NONCONSERVATIVE
Net work done by the force on an moving object around any closed path is zero
Friction
work done depend on starting ad ending point and path taken
Take energy away from the system as the system progresses
POTENTIAL ENERGY
energy stored in a body or system because of its position, shape and state
depend on external force
Gravitational potential energy, U = mgy
depends only on the height of the object above the surface of the Earth
m : mass of a body
g : acceleration due to graviti
y : height of a body from initial position
MECHANICAL ENERGY
Work-gravitational potential energy theorem
the change in gravitational potential energy as the negative of the work done by the gravitational force
W = Uf - Ui
the sum of potential energy and kinetic energy is zero if the is no nonconservation energy
Elastic potential energy, Us
energy stored in in elastic materials as the result of their stretching or compressing
Fs = -kx
W = 01/2KXf^2 - 1/2KXi^2
E = K + U
K2 + U2 = K1 + U1
E = 1/2mv^2 + mgy
LAW OF CONSERVATION OF ENERGY
energy can't neither be created nor destroyed. Energy can only be transferred or changed from one form to another and the total amount remains constant
GRAVITATIONAL POTENTIAL ENERGY AND ESCAPE VELOCITY
POWER
rate at which work is done
P = W/t
Instantaneos power
P = dW/dt
1 W = 1 J/s
rate at which energy is transferred
P = E/t
1 hp = 746 W
also needed for acceleration and for moving against force of friction
P = F . v