# Physics - P4

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• Created by: L_Georgie
• Created on: 07-04-16 17:03
How do you work out the speed of something?
Speed = Distance travelled/time taken
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What instantaneous speed tell you?
It tells you the average speed of something just over a really short time period.
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On a distance-time graph what does the gradient represent?
The speed.
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What does a flat section mean on a distance-time graph?
A flat section means that the object is stationary.
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What do positive and negative distances mean?
The positive and negative distances stand for direction in which the object is moving.
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What is the difference between speed and velocity?
Speed is just how fast an object is moving but velocity is how fast an object is moving in a certain direction.
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What does an objects acceleration tell us?
Acceleration tells us how quickly an object speeds up. It is the change in velocity/speed n a certain amount of time.
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On a velocity-time graph what does the gradient represent?
The gradient shows the acceleration.
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What does a flat section mean on a velocity-time graph?
It means the object is moving at a constant speed.
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What is force measured in?
Newtons
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What do forces come in?
Interaction pairs of equal strength.
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What is a reaction force?
A force that reacts to a force being applied.
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What is friction?
Friction is a reaction force that acts against the moving object.
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How can you reduce friction between two objects?
Add a lubricant, like oil or grease between the two surfaces.
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Why do we need friction to walk?
Without friction we won't be able to 'push' with our shoes against the ground and move forwards.
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What represents force in a diagram?
Arrows
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What does the length of the arrow represent?
The size of the force.
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What forces act on an object that is put on a table?
The object pushes downwards of the table because of it's weight, this causes an equal and opposite reaction force for the table pushing back up on the object.
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What is the resultant force?
The resultant force is the overall force acting on an object.
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Why is the resultant force important?
It decides the motion of the object - whether it will accelerate, decelerate or stay at a steady speed.
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How does a car accelerate?
The cars engine exerts a bigger driving force than the drag counter force.
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What is momentum?
Momentum is how hard it would be to stop an object from moving.
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How do seat belts reduce the chance of injury in a car?
Seat bells stretch slightly which increases the time taken for the wearer to stop, this reduces the forces acting on the person.
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What other safety features in a vehicles are designed to increase the collision time?
Crumple zones, air bags and helmets.
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What does work done mean?
The amount of energy transferred to another object.
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What has kinetic energy?
Anything that is moving.
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How do you increase an objects kinetic energy?
Increase it's velocity by applying a force to it.
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Can you create or destroy energy?
No it just gets transformed into another type of energy.
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What is Gravitational Potential Energy?
G.P.E is the energy stored in an object when you raise it to a height against the force of gravity.
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What happens to an objects G.P.E when you lift it up?
It increases.
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What happens to an objects G.P.E what it falls?
It decreases.
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What happens when an object falls?
It converts it's G.P.E into K.E.
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## Other cards in this set

### Card 2

#### Front

What instantaneous speed tell you?

#### Back

It tells you the average speed of something just over a really short time period.

### Card 3

#### Front

On a distance-time graph what does the gradient represent?

### Card 4

#### Front

What does a flat section mean on a distance-time graph?

### Card 5

#### Front

What do positive and negative distances mean?