P2- Work, energy and momentum Flashcards
How can work done be calculated?
W= F x d
W= work done in joules (J).
F= force in newtons (N).
d= distance in metres (m).
Work done to overcome friction is mainly transferred into energy by…
Heating. e.g: heat from brake pads when brakes are applied.
What is gravitational potential energy?
GPE is energy stored in an object because of its position above the surface of the Earth.
How can we calculate change in GPE?
GPE= m x h x g
m= mass in kg.
h= height in m.
g= gravitational field strength in J.
Define power.
The rate of transfer of energy.
How can power be calculated?
P= E/t
P= power in watts (W).
E= energy in joules (J).
t= time in seconds (s).
What does kinetic energy depend on?
- Mass of object.
- Object’s speed.
How can kinetic energy be calculated?
Kinetic energy= (1/2) x m x v2
m= mass in kg.
v= speed in m/s.
What is elastic potential energy?
Energy stored in an elastic object when work is done on the object.
What is the law of conservation of momentum?
Total momentum before is equal to total momentum afterwards- provided no external forces act on them.
Before= After.
How can we calculate momentum?
p= m x v
p= momentum in kg m/s.
m= mass in kg.
v= velocity in m/s.
What is momentum measured in?
Kilogram metres per second, kg m/s.
What is the total momentum after an explosion equal to and why?
In an explosion the objects move apart with equal and opposite momentum.
One momentum is positive and the other is negative, so total is zero.
What are crumple zones/what do they do?
Crumple zones in cars are designed to fold in a collision.
This increases the impact time, so reduces the force on the car and people inside it.
What is impact time?
Time taken for a collision to take place.
