# Forces

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• Created by: allieal
• Created on: 22-12-13 09:58
What is the measure of force?
Newtons (N)
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What does 'action and reaction' forces mean?
Objects always equal and opposite forces on each other
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What is a force?
A force can change the shape of an object or change its motion or state of rest.
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What is resultant force?
The single force that would have the same effect on the object as all the original forces acting together
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When is an objects resultant force zero?
When the object is stationary, When the object is moving in the same direction at constant speed
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What is the effect of a resultant force in the opposite direction on an object?
The object will decelerate
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What is the effect of a resultant force on an object at rest?
It will accelerate in the direction of the resultant force
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What equation links force, mass and acceleration?
Force (N) = Mass (kg) x Acceleration (m/s squared)
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What happened when mass increased and force remains constant?
Acceleration is smaller
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What 2 forces oppose a cars driving force?
Friction & Air Resistance
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What is stopping distance?
thinking distance + breaking distance
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What is thinking distance?
time for a driver to apply brakes, increased if driver if tired or under influence of drugs
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What is braking distance?
Time for a car to get to stationary after brakes are applied, increased by condition of car, conditions on the road
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What is weight?
the force of gravity
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What does f=ma become using weight?
Weight (N)= Mass (kg) x Acceleration due to gravity (m/s squared)
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What is gravitational field strength?
Energy of an object due to its position in a gravitational field. units are N/kg
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What is a drag force?
Upwards force of a fluid resisting an object falling
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How does an object reach terminal velocity?
As an object falls through a fluid a drag force resists its motion. The faster the object falls, the bigger the drag force becomes. Eventually drag force=weight of object and resultant force =zero. The constant speed is called terminal velocity
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What is an extension?
Extension is the different between the length of the spring and its original length
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What is an elastic object?
An object that regains its original shape when the forces deforming it are removed
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What is extension directly proportional to?
Force (N)- causes a straight line through the origin
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What is Hooke's law?
Extension is directly proportional to force applied, provided the limit of proportionality is not exceeded. Force (N) = k (spring constant, N/m) x Extension (m)
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What is the purpose of anti-skid surfaces?
Increase friction between a car tyre and road surface, reduces and sometimes prevents skiding
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What are average speed cameras?
Linked pairs of cameras that work out a cars average speed in between the two points.
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## Other cards in this set

### Card 2

#### Front

What does 'action and reaction' forces mean?

#### Back

Objects always equal and opposite forces on each other

What is a force?

### Card 4

#### Front

What is resultant force?

### Card 5

#### Front

When is an objects resultant force zero?