Forces

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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Forces

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