P2.4 Momentum, Energy, Work and Power Flashcards
What is the braking distance?
The time it takes for the brakes to bring the car to a stop.
What is the stopping distance?
Stopping distance= braking distance + thinking distance.
It is the total time it takes for the car to stop.
What factors effect the stopping distance?
- The mass of the vehicle
- The speed of the vehicle
- The driver’s reaction time
- The state of the vehicle’s brakes
- The sate of the road
- The friction
What is momentum?
It is a measure of motion.
Momentum= mass x velocity
Why is momentum a vector quantity?
Because velocity is a vector quantity, so momentum must be too because velocity is a factor of it.
What is linear momentum conservation?
When an object collides with another object, the goal momentum of both objects is the same before the collision as it is after. Therefore if a vehicle hits a barrier which has zero momentum, the velocity of the barrier and the car is the same, but the momentum of the car is less than belfry.
Why do we need seat belts?
When you are travelling in a car you have the same momentum as it. If the car stops, your momentum continues to carry you forward, so if it stops suddenly the force you hit the dashboard with can cause serious injuries. The faster the momentum of an object changes the greater the force on the object. In an accident a seat belt stretches, which reduces the change of momentum and therefore the force exerted on a person in the car.
What are other ways cars safeguard us against a dramatic change in momentum.
Airbags decrease the momentum more slowly so help to eleventh seatbelt injuries.
Cars also have crumple zones which fold in a specific way so that the momentum of the car changes over a longer period of time.
What is the equation for force?
Force= change in momentum/ time
What is work?
Work is when energy is transferred from one form to another. It is measured in joules, and the work done is equal to the amount of energy transferred.
What is the equation for work done?
Work done= force x distance moved (in direction of the force)
What is power?
Power is the rate at which work is being done.
What is the equation for power?
Power= work done/time. It is measured in watts.
What is the work done when stopping a vehicle?
Braking force x braking distance. The work done is equal to the vehicle’s initial kinetic energy.
What is gravitational potential energy?
The energy that is stored because of an object’s position in a gravitational field. If something can fall it has gravitational potential energy.
