Flashcards in P3 Deck (41):
How can you calculate speed?
Distance traveled ➗ time taken
What is the triangle for distance, speed and time?
S ✖️ T
How can you calculate the speed of a car from pictures taken by a speed camera?
Speed of car=
Distance travelled between pictures
Time taken between pictures
What is acceleration measured in?
- metres per second squared
How can you calculate the acceleration of an object?
Change in speed ➗ time taken for change
What is Relative speed?
- the speed of an object, relative to another object that is being treated to be at rest
Give an example of something weight causes?
- weight causes an apple falling from a tree to speed up as it falls
Give an example of something Friction causes?
- friction causes a car to slow down
How do you work out Resultant force?
Resultant force= mass(kg) ✖️ acceleration
How can you work out stopping distance?
Thinking distance ➕ braking distance
What is thinking distance?
- the distance travelled by the vehicle from the point the driver realises he needs to brakes to when he applies the brakes
What is Braking distance?
- the distance it takes the vehicle to stop once the driver applies the brakes
What can increase a vehicles braking distance?
- If the mass of the vehicle is increases, a loaded vehicle has a greater kinetic energy
- if the friction between the tyres and the road is decreased, a wet or greasy road surface reduces the amount of friction.
- if the braking forces applied is decreased, a smaller force is exerted by the brake pads on the wheel if the wheel discs if the pads are worn
- if the vehicle is travelling faster
How can the thinking distance of a car stopping be increased?
- if the vehicle is travelling faster
- if the driver is ill, tired, or under the influence of alcohol or drugs
- if the driver is distracted or isn't concentrating
How do you calculate the weight of an object?
Weight = mass ✖️ gravitational field
What is work done equal to?
- the energy transferred
What does the amount of work done depend on?
- the size of the force
- the distance the object has moved
How can you calculate the work done?
Work done =
Force applied ✖️ distance moved in direction of force
What is power a measurement of?
- how quickly work is done
How can you work out power using work done and time?
Power = work done ➗ time
How can power be calculated using force and velocity?
Power = force ✖️ velocity
What is kinetic energy?
- the energy an object has because of its movement
What does kinetic energy depend on?
If a car moves at a greater speed, or has a greater mass, how is the kinetic energy affected?
- the kinetic energy is greater
How can you calculate kinetic energy?
Kinetic energy =
1/2 ✖️ mass ✖️ speed squared
What does fuel consumption depend on?
- the energy required to increase the kinetic energy
- the energy required to work against friction
- driving style, speed and road conditions
How can frictional forces be reduced?
- changing the shape of the object
- using a lubricant
Name the 4 safety features cars have?
- seat belts
- crumple zone
- collapsible steering column
What is a cars safety cage?
- a metal cage which strengthens the cabin section of the car.
- prevents the vehicle from collapsing when upside down or rolling
Name the two safety features on a car which prevent accidents?
- anti lock braking system, prevent tyres from skidding
- traction control, prevents car from skidding when accelerating
What is momentum?
- a measurement of the state of motion of an object as a product of its mass and velocity
What happens to a cars momentum when the car slows down?
How can you work out momentum?
Momentum= mass✖️ verlocity
How can you calculate the force of momentum?
Change in momentum ✖️ time taken
How can the stopping forces experienced in a collision be reduced?
- increasing the stopping collision time
- increasing the stopping or collision distance
What happens when a skydiver jumps, before the parachute opens?
1- when the skydiver jumps, he is initially accelerates due to the force of gravity.
2- as he falls, he experiences the frictional force of air resistance in the opposite direction, at this point, weight is greater than resistance, so, he continues to accelerate.
3- as his speed increases so does the air resistance working against him.
4- air resistance increases until it is equal to weight, the resulting force now acting on him is zero and his falling speed becomes constant, this is TERMINAL SPEED
What happens when a skydiver jumps, after the parachute opens?
1- when the parachute is opened, unbalanced forces act again because the upwards force of resistance is greatly increased and bigger that weight
2- the increase in resistance decreases his speed
3- resistance decreases until it is equal to weight, a new TERMINAL SPEED is created
What is the gravitational potential energy of an object?
- the energy stored due to:
> it's mass
> it's position in the Earths gravitational field
How can you calculate Gravitational potential energy?
Mass ✖️ gravitational field strength ✖️ vertical height
What isEarth's Gravitational field strength?
> every 1kg of matter near the Earths surface expire cars a downward force of 10N