Summary Work, Energy and Power

WORK ENERGY AND POWER

WORK
Work – the product of the displacement and the component of the force acting
parallel to the displacement


W = FcosθΔxx
W = work done on object (J)
F = component of force acting parallel to displacement (N)
Δxx = displacement (m)
θ = angle between applied force and displacement


Whenever work is done energy is transferred from one object to another
Work done = energy transferred


POSITIVE AND NEGATIVE WORK
 Whether energy is transferred to or removed from depends on the
direction of the force and its displacement
 Only components of force acting parallel to displacement count as work
 Force same direction = energy transferred to = positive work
 Force opposite direction = energy removed from = negative work

, GRAVITATIONAL POTENTIAL ENERGY
Gravitational potential energy – the energy an object possesses due to its
position relative to a reference point


Ep = mgh


m = mass (kg)
g = 9.8
h = height (m) # All of these values are scalars


KINETIC ENERGY
Kinetic energy – the energy an object has as a result of its motion


Ek = ½ mv2


m = mass (kg)
v = velocity (m.s-1)


MECHANICAL ENERGY
Mechanical energy – the sum of the gravitational potential energy and kinetic
energy at a point


Emech = Ep + Ek