2.3 Work, Energy And Momentum Flashcards
What is work done? Unit?
Energy transferred
Joules (J)
Work done to overcome friction is mainly transferred into energy by what?
Heating
What is gravitational potential energy?
Energy stored in an object because of its position in the earths gravitational field
When does an object gain Gravitational potential energy?
When it is moved vertically upwards
What is the gravitational potential energy equal to when it is moved vertically up?
Equal to work done on it by the lifting force
Unit for…
Gravitational potential energy
Gravitational field strength
Joules (J)
Newtons per kilogram (N/kg)
What is power?
The rate of transfer of energy
Or
Work done in a given time
Unit of power?
Watts (W)
What do all moving objects have?
Kinetic energy
What is momentum?
A property of moving objects
What happens to momentum in a closed system?
It is conserved in a closed system i.e no other external force are involved
Momentum involves mass and velocity, can momentum be negative? Explain?
Velocity can be negative if it goes in the opposite direction
Therefore momentum can be as well
Unit of momentum?
Kg m/s
What happens in an explosion?
Two objects move apart with equal and opposite momentum
As
One momentum is positive and the other is negative
Making the total monument zero
What is an example of an explosion?
A gun
The bullet fires off with momentum in one direction
The gun recoils with equal momentum in the opposite direction
What happens to momentum in a collision?
Often becomes zero during impact
If the impact time is short what happens to the force?
It is large
If the impact time is longer what happens to the force?
It decreases
What does a crumple zone do in a car?
It folds in a collision
Increasing the impact time so it reduces the force on the car and the people in it
What other safety features do cars have?
Airbags: spread the force across a wider surface area
Seat belt: increases impact time which reduces the force
