P2 - Momentum Flashcards
What is the unit of momentum?
Kg m/s
What is the formula for momentum?
P = mv Momentum = mass * velocity
If a mass of 20kg was travelling at 10m/s, what would the momentum be?
200 kg m/s
Is momentum a vector or a scalar?
Vector
What is meant by “momentum is conserved”?
That momentum can’t be created or destroyed, it is only passed on
If two objects of the same mass collided at the same velocity, the momentum would be 0kg m/s
Explain how this is possible
Momentum is a vector meaning there is a direction
In this case, the momentum is 0kg m/s because there is no resultant direction to the momentum
How do we calculate change in momentum?
m(v - u)
Mass * (Final velocity - Initial velocity)
How do you calculate the rate of change in momentum?
m(v - u) / t
(Mass * (final velocity - initial velocity)) / time
How are force and momentum linked?
Force is the rate of change in momentum
When an object hits another object and then stops, where is the momentum?
All of the momentum is in the other object that has been hit
If an object hits another object and they both travel together, where is the momentum?
The momentum is in both objects
If the masses of the objects were the same, the final velocity would be half the initial velocity
What is the equation that shows the conservation of momentum?
Resultant momentum before = resultant momentum after
What are the 2 types of collision?
Elastic
Inelastic
What happens to kinetic energy in elastic collision?
The kinetic energy is completely conserved
What happens to momentum in an inelastic collision?
The kinetic energy is dispersed as other types of energy
What is the formula for kinetic energy?
1/2 * mass * velocity^2
1/2mv^2
How are force and momentum related?
Force is the rate of change of momentum
Why are car crashes dangerous in terms of momentum and how are cars designed to take this into account?
In a car crash, momentum changes very quickly meaning that the forces in the body are very large (because force is rare of change of momentum)
Cars are designed to slow people down over a longer time when they crash so that the rate of change of momentum is smaller
Describe the 4 ways that cars prevent injury in car crashes
Crumple zones at the front and back of the car crumple on impact which increases the impact time decreasing the force
Seat belts stretch slightly increasing the time taken for the wearer to stop
Side impact bars are strong metal tubes that direct the kinetic energy of the crash away from the passengers to areas of the car
Air bags slow you down more gradually and prevent you from hitting hard surfaces of the car
How do regenerative braking systems work?
Rather than converting the kinetic energy to heat energy in brakes, it puts the motor in reverse
This slows the wheels and the motor acts as an electric generator to convert the kinetic energy into electrical energy which is stored as chemical energy in the battery
