Physics Flashcards
In a distance time graph how is : Speed represent Stationary/stopped represented How fast Going backwards Acceleration and deceleration Speeding up Slowing down
Speed - gradient Stationary - flat line How fast - steeper the graph Going back - downhill sections Acceleration/deceleration - curved lines Speeding up - steepening curve Slowing down - levelling off
What is the difference between speed and velocity
Speed is how fast you are going (e.g 30mph or 20m/s)
Velocity how fast you are going in a given direction (e.g 20m/s north)
How to calculate speed on distance time graphs
Speed = gradient = vertical/horizontal
E.g 500/30 = 16.7
What is acceleration
Acceleration is how quickly a velocity is changing
What is the acceleration formula
Acceleration = change in velocity / time OR Acceleration = (v-u) ----- a x t V= final velocity U= initial velocity
In a velocity time graph how is Acceleration is represented Steady speed Acceleration/deceleration Distance travelled in a time interval Changing acceleration
Acceleration- gradient
Steady speed- flat sections
Acceleration- uphill sections
Deceleration- downhill sections
Distance travelled in a time interval - the area under any section of the graph
Changing acceleration- curve
How do you calculate acceleration from a velocity time graph
Acceleration=gradient= vertical change/horizontal change
How do you find out velocity from a velocity time graph
Simply found by reading the value of the velocity axis
How do you find the distance travelled on a velocity time graph.
It is equal to the area under the graph
What is gravitational force
It is the force of attraction between all masses
Gravity gives every thing a ……..
Weight
Gravity make all things accelerate towards the ground
What is the approximate acceleration ?
10m/s. ( on earth )
What is the difference between weight and mass ?
Mass - the amount of stuff in a object for any given object on any universe
Weight- is caused by the pull of gravitational force
The weight of an object is just the force pulling it towards the centre of the earth
What is the difference between weight on a different planet and mass on a different planet
Mass is the same any where on the universe
Weight is different depending on where it is
E.g 1kg mass will weigh less on the moon (1.6N) than it does on earth (10N) simply because the gravitational pull is less.
What is the unit for measuring gravity
And what is the equipment used for it
The unit for measuring gravity is: Newtons
It is measured using a Newton meter or a spring balance
What is the unit for mass
Kg (kilograms)
What is the formula for weight
Weight = mass x gravitational field strength
What is the units for weight
Newtons
What is earths gravitational field strength
g = 10N/kg
g - strength of gravity
What is the earths gravitational field strength
1.6 N
What is the resultant force
The overall force on a point or object
There are normally ……… Forces acting on a object
2 forces
The overall effect of these will decide its motion
E.g accelerate, decelerates or stays at a steady speed
If the forces are all acting along the same line
E.g parallel or opposite
how do you work out the overall force
Adding or subtracting them
E.g the resultant force on a stationary teapot with 10N pushing up and 10N pushing down
Then 10N - 10N = 0N
If something is stationary then all the forces are …..
Balanced
What does a resultant force mean ?
Not definition of what it is
It means a change in velocity
As if there is a resultant force acting on a object then it will change its state of rest or motion
If a car has a driving force of 1000N and a air resistance of 600N. Then what is the resultant force
400N
Because 1000N - 600N = 400N
If a resultant force on a stationary object is zero, the the object will …………. …………..
Remain stationary
If there is no resultant force there is no change in what ?
Velocity
If there is no resultant force on a MOVING object then …………..
The object will carry on moving at the same velocity
Formula for resultant force
F = ma. OR. A = f/m
F - resultant force in newtons
M - mass in kilograms
A - acceleration in meters per second square
What are reaction forces
When two objects interact the forces they exert on each other are equal and opposite
What is friction
Friction always slows things down
Friction always act in the opposite direction to movement
How to you get friction
Friction happens when there are two surfaces in contact
Or when a object passes through a fluid (drag)
How can you reduce drag
Keep the shape of the object streamlined
When does drag increase
When speed increases
How does terminal velocity work
- the object starts to fall
- The force of gravity is much more than the frictional force
- As the speed increases the friction builds up this gradually reduces acceleration
- Eventually the frictional force becomes equal to the accelerating force.
- This is when it reaches the maximum speed or terminal velocity
The terminal velocity of a object depends on it ………… And ……………
Shape and size
What is stopping distance
The total stopping time of a vehicle is the distance covered in the time between the driver first spotting a hazard and the vehicle coming to a complete stop.
What is thinking distance
The distance the vehicle travels during the drivers reaction time
Reaction time is the time between the driver spotting a hazard and taking action
What are the 2 factors that effect thinking distance
- How fast you are going
2. How dopey you are . E.g tiredness, drugs and drunk
What is braking distance
The distance the car travels under the breaking force.
What are the 4 main factors that effect braking distance
- How fast you are going
- How good your brakes are (minimum tread depth 1.6mm)
- How good the tyres are
- How good the grip is
What is meant by ‘ work done ‘
When a force moves an object through a distance ENERGY IS TRANSFERRED and WORK IS DONE
( basically when something moves something else is providing some sort of effort to move it )
What is the formula for work done
Work done = force x distance
What is gravitational potential energy
Is the energy that a object has by virtue of its vertical position in a gravitational field
(Work is done against the force of gravity because of the effort needed to lift a object. Which gains the object gravitational potential)
What is the formula for gravitational potential
Gpe = mass x g x height
Gpe = gravitational potential energy
What is kinetic energy
The energy of movement
What is the formula for kinetic energy
Kinetic energy = 1/2 x mass x speed
What does Ep stand for ?
It stands for gravitational potential energy
Ep and gpe are the same thing
What is the law on conservation of energy
Energy cannot be created or destroyed but only converted into different forms
Kinetic energy transferred is ……… ………..
Work done
(For example when a car is moving it has a lot of kinetic energy.to slow the car down the kinetic energy needs to be converted into other types of energy)
What is the formula for kinetic energy transferred
Kinetic energy transferred = work done by brakes
1/2mv² = F x D
M= mass of car passenger in kg V= speed of car m/s F= maximum braking force in Newtons D= braking distance in meters
What happens when something falls
It’s potential energy is converted into kinetic energy
so the further it falls the faster it goes
What is the formula for kinetic energy gained
Kinetic energy gained = potential energy lost
Some kinetic energy is converted into ………. And ……….
Heat and sound
What happens when work is done to an elastic object
It is stored as elastic potential energy
When you apply a force to a object you may cause it to ……….. And …………. …… ………
Stretch and change shape
What is an object called if it can go back to its original shape after the force has been removed
An elastic object
When work is done to an elastic object to change its shape what happens to the energy
It is NOT lost but is stored by the object as elastic potential energy which is then converted to kinetic energy when the force is removed and the object returns back to original shape
E.g a spring or elastic band bouncing back
Extension of a elastic object is directly proportional to …………..
Force
E.g the extension of a spring is directly proportional to the load of force applied
What is the formula for force
F= k x e
K= spring constant E= extension