# P2.2.6 Streching and Squashing + P2.2.7 Force and speed issues

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• Created on: 04-05-14 19:25
How do we measure the extension of an object when it is streched?
The extension is the distance between the length of the spring and its original length.
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How does the extension of a spring vary with the force applied to it?
The extension of a spring is directly proportional to the force applied to it, provided the limit of proportionality is not exceeded.
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What is the spring constant of a spring?
The spring constant of a spring is the force per unit needed to strech it.
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How can we tell when a spring has exceeded its limit of proportionality?
The graph of extension against force applied is no longer a straight line.
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What is the equation used to work out the force?
Force (N) = spring constant (N/m) x extension (m)
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How can the fuel economy of road vehicles be improved?
Fuel economy of a vehicle can be improved by reducing the speed or fitting a wind detector (making the vehicle more streamline).
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Why does making a vehicle more streamline improved fuel economy?
Less energy force and less power are needed to maintain a certain speed. Less fuel is needed so the fuel costs are reduced.
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Why are speed cameras sometimes used in pairs?
Speed cameras are sometimes used in pairs to determine the speed at two points and calculate the average speed.
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When does skidding occur?
Skidding happens when the brakes on a vehicle are applied too harshly.
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How does skidding affect the stopping distance of a vehicle?
Skidding increases the stopping distance.
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What is used to prevent skidding?
Anti-skid surfaces.
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How do anti-skid surfaces reduce skidding?
They are rougher than normal road surfaces and increase the amount of friction between the tyres and the road.
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Where are anti-skid surfaces usually put?
They are used in places where drivers are likely to brake such as near traffic lights and road junctions.
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## Other cards in this set

### Card 2

#### Front

How does the extension of a spring vary with the force applied to it?

#### Back

The extension of a spring is directly proportional to the force applied to it, provided the limit of proportionality is not exceeded.

### Card 3

#### Front

What is the spring constant of a spring?

### Card 4

#### Front

How can we tell when a spring has exceeded its limit of proportionality?

### Card 5

#### Front

What is the equation used to work out the force?