# P4-Explaining motion

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• Created by: Naana
• Created on: 30-05-14 16:08
What is the formula for working out speed?
Distance travelled (m)/time taken (s)
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What does the gradient of a distance time graph tell you?
The speed
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What’s the difference between speed and velocity?
The speed is the measure of how fast something is going. Whereas velocity is a more useful measure of motion as it describes both the speed and direction
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What is instantaneous velocity?
This is the speed and direction at a given moment of time
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What is acceleration?
This is the change in velocity or speed in a certain amount of time
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What is an interaction pair?
When an object exerts a force on another object and it experiences a force in return
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What is friction?
When an object is moving relative to one another and both objects experience a force in the direction that opposes the movement.
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Why is friction a reaction force?
Because it happens as a result of an applied force
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What is meant by resultant force?
This is the overall force acting on an object-the force you get when you add all the individual forces and their directions.
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What results in an increased acceleration?
The bigger the resultant force, the greater the acceleration
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What does it mean if a resultant force is zero?
It means that the stationary object will stay still.
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Explain how air bags, seat belts and crumple zones reduce the risk of serious injury in a car crash
Air bags slow you down more gradually, seat belts stretch slightly increasing time taken for the wearer to stop which reduce the forces acting on your chest and crumple zones crumple impact which increase time taken for car to stop.
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Explain how work done is energy transferred
When a force moves an object it does work and energy is transferred to the object
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What is kinetic energy?
This is the movement energy. Anything that moves has kinetic energy. The greater the mass and the faster something’s going, the greater the kinetic energy.
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What is gravitational potential energy (GPE)?
This 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 when an object falls?
It’s gravitational potential energy is converted into kinetic energy.
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## Other cards in this set

### Card 2

#### Front

What does the gradient of a distance time graph tell you?

The speed

### Card 3

#### Front

What’s the difference between speed and velocity?

### Card 4

#### Front

What is instantaneous velocity?

### Card 5

#### Front

What is acceleration?