Forces and Motion Flashcards
Definition of vector quantity
Magnitude and direction
Definition of scalar quantity
Only magnitude
Definition of speed
Just how fast you are going
Definition of velocity
Speed in a given direction
Walking speed
5km/h
Running
11km/h
Cycling
20km/h
Cars in a built-up area
47km/h
Aeroplanes
900km/h
Cars on a motorway
112km/h
Trains
200km/h
Wind speed
5 - 20 m/s
Speed of sound in air
340m/s
Ferries
54 km/h
Definition of acceleration
How quickly something is changing speed
Average acceleration formula
acceleration = change in velocity / time
Uniform acceleration definition
Constant acceleration
Uniform acceleration formula
final velocity squared - initial velocity squared = 2 x acceleration x distance
Gradient in distance-time graph
Speed
Curves in distance-time graph
Acceleration
Gradient in velocity-time graphs
Acceleration
Curves in velocity-time graphs
Changing acceleration
Area underneath line in velocity-time graph
Distance travelled
Newton’s First Law
A resultant force is needed to change motion of an object
5 ways to “accelerate”
Stopping Starting Slowing down Speeding up Changing direction
Newton’s Second Law
The larger the resultant force, the more the object accelerates
Formula to remember Newton’s Second Law
Force = mass x acceleration
Why are large declarations dangerous?
Large declarations require a large force (f = m x a)
How to decrease force in a crash?
Increase time for car to decelerate so less force is required for it to stop
Definition of mass
Amount of matter an object has
Definition of weight
Force acting on an object due to gravity
Weight of formula
Weight = mass x gravitational field strength
What does gravitational field strength rely on?
Distance from object causing field
Mass of object causing field
Centripetal force
Force that keeps something moving in a circle
Why is a object travelling in a circle constant accelerating?
It is always changing direction, so it’s velocity is always changing
Newton’s Third Law
The forces two objects exert on each other are equal and opposite
Inertia definition
Tendency for motion to remain unchanged
inertial mass
measures difficulty for an object to change its velocity
intertidal mass formula
m = F / a
Momentum
Tendency for an object to keep moving in the same direction
Momentum formula
momentum = mass x velocity
Conservation of momentum
Total momentum before = total momentum after (in a closed system)
Stopping distance definition
Distance covered between the driver first spotting a hazard and vehicle coming to a complete stop
Stopping distance formula
Stopping distance = thinking distance + braking distance
Factors affecting thinking distance
- reaction time (tiredness, alcohol, drugs, distractions)
- speed
Factors affecting braking distance
- speed
- mass of vehicle
- conditions of brake
- friction between tyres and road
Thinking distance as speed increases
Thinking distance increases at the same rate
Braking distance as speed increases
Braking distance increases by a square e.g. 2 -> 4, 3 -> 9
work down by brakes formula
Work done by brakes = 1/2 x mass x speed of car squared
Energy in car’s kinetic energy store formula
1/2 x mass x speed of car squared = braking force x braking distance
All energy stores
Kinetic Thermal Chemical Gravitational potential Elastic potential Electrostatic Magnetic Nuclear
Factors affecting kinetic energy store
Speed
Mass
Kinetic energy formula
kinetic energy = 0.5 x mass x speed squared
Factors affecting gravitational potential energy
Height above the mass causing the gravitational field
Mass of the object
Gravitational field strength
Gravitational potential energy formula
GPE = mass x gravitational field strength x change in vertical height
