# P3 Physics

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- Created by: Lydia1
- Created on: 20-01-13 16:51

What is the equation for Average speed?

AVERAGE SPEED=(U+V) divided by 2

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What does U and V mean in an equation?

U=speed at the start V=speed at the end.

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On a Distance/Time Graph what does the gradient show?Flat sections?Curves?'Downhill sections?

Gradient=Speed Flat section=Object has stopped Curves=Acceleration and Deceleration Downhill=Change in direction.

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The steeper the gradient on a distance/time graph.....

The faster the object is going

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What is acceleration?

How quickly the speed is changing ---ACCELERATION=CHANGE IN SPEED divided by TIME TAKEN

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On speed/time graphs, what does the gradient show?Flat sections?Curves?Downhill sections?Uphill?

Gradient=Acceleration Flat sections=Constant speed Curves=changing acceleration/deceleration Downhill=deceleration Uphill=Acceleration

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What does the area under the graph on a speed/time graph show?

The distance travelled in that time space.

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WHat is the difference between speed and velocity?

Speed-how fast an object is going Velocity-how fast an object is going and in which direction.

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What is the difference between mass and weight?

Mass-The amount of things inside an object Weight-The pull of gravity on an object.

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What is the equation for weight?

Weight=massxgravitational field strength

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What is the gravitational files strength of an object?

The acceleration of the object due to gravity.

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Which directions does the gravity and weight force act?

Downwards

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Which direct does a reaction force act?

Upwards

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What does a push or pull force do?

Speed up an object

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What does drag, air resistance and friction do?

Slows an object down.

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What forces are acting on a stationary object?

Gravity and reaction forces are equal and the two horizontal forces are equal too.

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What forces are acting on an object with a steady speed?

For an object moving horizontally-Weight,Reaction,Drag and thrust are equal For a falling object-Weight=drag

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What forces are acting on an accelerating object?

Horizontally moving-Thrust must be bigger than drag Vertically moving- Weight must be bigger than drag

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What are the three main ways where friction occurs?

1.Between two solid surfaces that are gripping.2.Two solid surfaces that are sliding past each other.3.Resistance from fluids(.e.g streamlined vehicles)

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In a fluid, as the speed increases...

The friction increases.

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What is the terminal speed of an object?

When an object first sets off(.e.g falling) acceleration is greater than drag so it will move quickest. It will reach its maximum speed which is its terminal speed.

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What does the terminal speed of an object depend on?

The amount of drag on the object and the drag depends on the shape and area(e.g a skydiver with a parachute)

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If the forces on an object are all balanced....

The object will move at the same speed in the same direction

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If there is an unbalanced force on the object...

The object will accelerate in the direction where there is most force.

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What is the resultant force?

The unbalanced force

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What is the equation for the resultant force?

The resultant force=Massxacceleration

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What is the equation for stopping distance?

Stopping distance=Thinking Distance + Breaking Distance

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What is Thinking Distance?

The distance the car travels between the driver noticing when to stop and applying the brakes

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What is Braking Distance?

The Distance taken to stop once the brakes have been applied

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What affects Thinking distance?

1.The speed that you are travelling at 2. Your brain activity-tiredness,alcohol, distractions, concentration.etc.

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What affects braking distance?

1.The speed you are travelling at.2.The conditions of your brakes.3.The weight your car is carrying.4.The grip between the tyres and the road

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What affects the grip between the tyres and the road?

1.Weather conditions(wet/icy roads are slip) .2.Road surface(dirt/leaves on the roads).3.The tyres(They must have a tread depth of 1.6mm to get rid of water)

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Why are speed limits important?

They affect the stopping distance which allows you to leave enough space between your car and the one in front as you stop the car.This avoids any accidents.

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WHat does speed affect more, Braking distance or thinking distance?

Braking distance because as the speed increases, the braking distance increases faster than thinking distance

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What is the relationship between speed and braking distance?

A squared relationship.e.g if the speed doubles, the braking distance increases by 4-fold(because 2 squared is 4)

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What is the equation for momentum?

Momentum(kgm/s)=mass(kg) x velocity(m/s) -----the greater the mass of an object and the greater the velocity, the more momentum the object has

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What happens when a force acts on an object?

It changes its momentum-- Force acting(N) = change in momentum(kgm/s) DIVIDED BY time taken for the change to happen

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How does the momentum in a car crash cause a persons injury?

As the momentum changes very quickly, the forces on the persons body will be big which means it is likely to cause injury.

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How are cars designed to reduce injury in a car crash?

They are designed to slow the people in the car down because if the change in their momentum is slower, then the forces on their body will be smaller so there is less chance of injury.

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How do crumple zones on a car work?

They change shape when they hit another object which increases to time it takes for the car to stop so there is less force acting on the car.

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How do seat belts work?

On impact, they stretch which increases the time taken for the person in the car to stop moving , therefore reducing the amount of forces acting on their body.

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How do ABS(anti-lock braking system) brakes work?

They pump on and off and stop the wheels locking and skidding . They also reduces braking distance.

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How do we test these safety features on the cars?

Using crash dummies with sensors at different parts of its body inside cars and crashing the cars.The sensors indicate were injuries would have been and then the results are compared with real life figures.

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How do we know that the safety features have been effective?

Seat belts reduce casualties by 50% / Airbags by 30%/ A reduction in no. of injuries since the 1980s

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What is the work done?

When a force makes an object move, energy is transferred and work is done

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What is the equation for Work Done?

Work Done= ForcexDistance

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What is Gravitational potential energy?

The energy that an object has due to its height above the ground. Gravitational potential energy(J)=Massx g(10N/kg) x-height

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WHat is kinetic energy and what does it depend on?

It is the energy that something has when it is moving. It depends on the mass and the speed of the object

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What is the equation for kinetic energy?

Kinetic Energy= 1/2 x mass x speed(squared) if you double the mass, you double the KE/ If you double the speed you quadruple the KE

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What is the equation for the kinetic energy transferred and work done by brakes?

1/2 x mass x speed(squared) = forces distance

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What is the relationship between kinetic energy and gravitational potential energy?

When an object falls, the gravitational potential energy is converted into kinetic energy so the further it falls the faster it goes. When the object reaches its terminal speed, the speed won't increase anymore so the kinetic energy wont either

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What is the equation to link kinetic energy and gravitational potential energy?

Kinetic energy gained= Gravitational potential energy lost ----1/2xmassxspeed(2) = massxgxheight

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what is power?

How quickly work is done Power=Work done (divided by) time taken

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What is power based on force and speed ?

Power=Force x Speed

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What is fuel consumption based on?

A more powerful machine means that there is more energy transferred from its fuel every second,therefore there is a higher fuel consumption

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A vehicle that has a higher fuel consumption...

Are more expensive as the fuel costs money/ More damaging to the environment as the fossil fuels pollute

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What affects fuel consumption?

The Mass of car(higher mass means you need more kinetic energy so more fuel)/Driving style(Faster accelerations use more energy)/Drag on the car

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What gases are released by the fuel?

CO2, Nitrogen Dioxide and Water Vapour

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What are biofuels?

They are a renewable source of energy that can be used in cars made from plants and organic waste.. Although they still produce CO2, the plants used to make them take in the CO2 so there is no increase.

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What are features of electric cars?

They need to be recharged using electricity from power stations that do cause pollution and they are expensive although they dont pollute during being used

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## Other cards in this set

### Card 2

#### Front

What does U and V mean in an equation?

#### Back

U=speed at the start V=speed at the end.

### Card 3

#### Front

On a Distance/Time Graph what does the gradient show?Flat sections?Curves?'Downhill sections?

#### Back

### Card 4

#### Front

The steeper the gradient on a distance/time graph.....

#### Back

### Card 5

#### Front

What is acceleration?

#### Back

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