Monentum, Energy, Work And Power Flashcards
What is the thinking distance
The distance a vehicle travels while the driver reacts to seeing the problem
What is the braking distance
The distance the vehicle travels from the position where brakes were first applied to where the vehicle is stationary
What is the stopping distance
The thinking distance + the braking distance.
What is reaction time and how can it be altered
The time it takes for someone to react to a stimulant. Several things can affect it such as drugs (stimulants and depressants) or being tired etc.
What things affect the thinking distance
The reaction time of the driver and the speed of the vehicle. If they are driving fast or have a large reaction time, the thinking distance will be increased
What affects braking distance.
Speed, friction from brakes, tyres, road etc, mass of vehicle.
If high speed, longer braking distance
If low friction, longer braking distance
If high mass, longer braking distance
What is momentum
A measurement of how strongly so,thing is moving
Momentum = mass x velocity
It a vector quantity and is in the direction if the velocity as that is also a vector quantity
What is conservation of linear momentum
When 2 objects collide, the total momentum of the 2 objects will be the same as the total momentum of the 2 objects after the collision. E.g. A car crashes into a barrier. The barrier at the start has no momentum as it is stationary. The barrier will start to move but the velocity of the barrier and vehicle will be less than the velocity on its own. It will have the same momentum however as there is added mass from the barrier
Why can momentum be dangerous
When you are in the car, you are travelling at the same speed as the car but if the car suddenly stops, your momentum will carry forwards a you may hit the dashboard which can cause serious injury
What safety features are in a car to try and reduce injury in crashes. List 3
Crumple zones at the front mean deceleration is less so less force is applied to the passenger
Seat belts lock and stretch to make sure you don’t fly out of your seat into the window.
Air bags deploy to reduce forces acting on the passenger
What is ‘work’
Work is done when energy is transferred from one form to another. It is the amount of energy transferred. It is measured in joules as work done is equal to the amount of energy transferred.
If a sailor moves a 300N sail up by 4M how much work has he done
Work done = force x distance moved
E = F x D
E = 300 x 4
E = 1200 joules
What is power in terms of work
Power is the rate of doing work and is measured in watts (W). 1 what equals one joule of work done per second.
P = E/t
Power (W) = work done (J) / time (seconds)
What is GPE
GPE is gravitational potential energy and is the amount of energy stored in an object depending on its position ( if it is high it will have more GPE than when it is lower)
GPE = mass(Kg) x gravitational field strength (Kg/n) x vertical height (M)
What is the GPE gained by a 500Kg object when dropped from 15M on earth
GPE = M x gravitational field strength x h GPE = 500 x 10 x 15 GPE = 75 000J
