Forces

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• Created by: Holly45
• Created on: 10-03-15 18:58

Forces between objects

• when 2 objects push or pull on each other they exert equal and opposite forces on one another
• unit of force is NEWTON (N)
• friction
• motive force
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Resultant forces

• when the resultant force on an object is zero, the object remains stationary or continues to move in the same direction and speed
• the resultant force is equal to the sum of the two forces and acts in the same direction as the 2 forces
• if an object is acted on by 2 unequal forces acting in different directions, the resultant force is equal to the difference between the 2 forces and in the direction of the larger force
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Force and acceleration

• F = M x A
• if the velocity of an object changes, it must be acted on by a resultant force
• the velocity of the object decreases if the resultant force is opposite in direction to its velocity
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• breaking force needed depends on the speed of the vehicle when the brakes were applied and the mass
• R = M x A : resultant force
• the thinking distance is the distance travelled by the vehicle in the time is takes the driver to react
• stopping distance = thinking distance + breaking distance

Factors affecting it:

• the faster the vehicle is travelling
• tiredness, drugs and alcohol
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Falling objects

• the weight of an object is the force of gravity on it
• the mass of an object is the quantity of matter on it
• weight = mass X gravitational field strength
• the object reaches a constant velocity when the drag force on it is equal and opposite to its weight. This is terminal velocity
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Hooke's law

• Force applied = spring constant X extension
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