P2.2 The Kinetic Energy Of Objects
Speeding Up Or Slowing Down
1 P2.2.1 Forces And Energy
1.1 When a force causes an object to move through a
distance work is done and energy is transferred.
1.1.1 W=F×d where W is the work done in joules, J, F is
the force applied in newtons, N and d is the distance
moved in the direction of the force in metres, m.
1.1.1.1 P=E/t where P is the power in watts,
W. E is the energy transferred in joules,
J and t is the time taken in seconds, s.
1.1.1.1.1 Ep=m×g×h where Ep is the
change in gravitational potential
energy in joules, J, m is the mass
in kilograms, kg. g is the
gravitational field strength in
newtons per kilogram, N/kg and h
is the change in height in metres, m
1.1.1.1.1.1 Ek=1/2×m×v2 where Ek is the kinetic
energy in joules, J, m is the mass in
kilograms, kg and v is the speed in metres
per second, m/s.
2 P2.2.2 Momentum
2.1 Momentum is a property of moving objects: p=m×v where p is momentum in kilograms metres per second, kg
m/s, m is the mass in kilograms, kg and v is the velocity in metres per second, m/s.
2.1.1 In a closed system the
total momentum before
an event is equal to the
total momentum after
the event. This is called
conservation of
momentum.