P2.2 Flashcards
work done
when a force moves an object , energy is transfered and work done.They are both measured in joules.
W = F × d
W is the work done in joules, J
F is the force applied in newtons, N
d is the distance moved in the direction of the fo
power
Power is a measure of how quickly work is being done and so how quickly energy is being transferred.
P = E ÷ t
P is the power in watts, W
E is the work done (or energy transferred) in joules, J
t is the time taken in seconds, s.
GPE
potential energy is the energy something gets when it is lifted.it is energy due to height.On earth gravi streghnth is 10N/Kg
Ep = m × g × h
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
h is the change in height in metres, m
kinetic energy
it is the energy that a moving has.The kinetic energy an object has depends on its:
Mass
Speed
Calculating kinetic energy
Here is the equation for calculating kinetic energy:
Ek = ½ × m × v2
Ek is the kinetic energy in joules, J
m is the mass in kilograms, kg
v is the speed in metres per second, m/s.
link between KE and GPE
kinetic energy gained= PE lost
when an object falls it transfers GPE into KE
momentum
A moving object has momentum. This is the tendency of the object to keep moving in the same direction
p = m × v
p is the momentum in kilograms metres per second,
kgm/s
m is the mass in kilograms, kg
v is the velocity in m/s
{negetive momentum is momentum in a different direction}
{when an object is stationarty it has a momentum of 0}
what does momentum depend on
Notice that momentum does not just depend on the object’s mass and speed. Velocity is speed in a particular direction, so the momentum of an object also depends on the direction of travel. This means that the momentum of an object can change if:
The object speeds up or slows down
The object changes direction
momentme conservation
As long as no external forces are acting on the objects involved, the total momentum stays the same in explosions and collisions. We say that momentum is conserved.
