P2.3 Flashcards
What causes the transfer of energy?
The work you do when working out.
What does the work done by a force depend on?
On the size of the fore and distance moved.
What is the equation for the work done?
=force applied(N) X distance moved in the direction of the force(m)
What is gravitational potential energy?
Energy stored in an object because of its position in the Earth’s gravitational field.
What happens to the gravitational potential energy when the object is moved up?
Increases.
What happens to the gravitational potential energy when an object moves down?
Decreases.
What is the equation for the change of potential energy?
=its weight(N) X change of height
Why must energy be supplied to the muscles?
To keep the muscles contracted.
What is the equation for the change in gravitational potential energy and mass?
=mass(kg) X gravitational field strength(N/kg) X change of height
What is power?
Rate of transfer of energy.
What is the equation for power?
P=E/t
What is the equation for kinetic energy?
=1/2 X mass(kg) X speed2(m/s)2
What does the kinetic energy recovery system do?
Stores energy in vehicles for when the vehicle brakes and uses it later.
When stretching a rubber band c what is the work done stored in it as?
Elastic potential energy.
What is elastic potential energy?
The energy stored in an elastic object when work is done on it to change its shape.
Who is momentum important to?
Anyone who plays contact sport.
What is the equation for the momentum of a moving object?
Momentum(kg m/s)=mass(kg) X velocity(m/s)
What does the law of conservation of momentum state?
The total momentum before an event is equal to the total momentum after the event.
In a front-end impact what happens to the momentum?
It’s reduced.
In a rear-end impact what happens to the momentum?
It’s increased.
Why does making the impact time longer reduce the impact force?
Momentum of the trolley would be lost over a longer time and it’s kinetic energy would be transferred over a greater distance.
What is the equation for the impact force?
=mass(kg) X deceleration
What happens when two vehicles collide?
They exert equal and opposite impact forces on each other at the same time.
What happens to the change of momentum when two vehicles collide?
The change of momentum is equal and opposite to the change of momentum of the other vehicle.
Why do seat belts reduce the force on people in car accidents?
Stops its wearer from continuing forwards when the car stops.
Why do air bags reduce the force on people in car accidents?
It spreads the force of an impact across the upper part of the body.
Why are ordinary car seat belts unsafe for children?
Because the seat belt won’t fully support them because it won’t fit around their whole body.
Name safety features in a car:
- front and rear seat belts
- airbags
- frogs and rear crumple zone
- side impact bars
