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Forces (A force is something that causes an object to move or change…
Forces
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Newton's first law states that unless a force acts on it, an object at rest stays at rest, and an object in motion stays in motion with the same speed and in the same direction.
The law of the lever states that when a lever is balanced the sum of the clockwise moments equals the sum of the anticlockwise moments.
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Newton's second law states that when a force acts on a mass, it accelerates. The greater the force, the greater the acceleration.
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Friction occurs when two surfaces are in contact. The rougher the surface, the greater the friction.
Examples of forces are weight, push, pull and friction.
To calculate the moment of force: Force x perpendicular distance from the fulcrum to the line of action.
Disadvantages of friction are: Causes moving parts in an engine to wear away. Causes burns when climbing ropes. Friction with the air slows down vehicles, reducing fuel efficiency.
Advantages of friction are: Allows a good grip between car tyres and road. Brakes in a car use friction to stop. Warms hands when they are rubbed together.
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The centre of gravity of an object is a point in the object through which all the weight of the object appears to act.
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Force arrows that are the same size means that the object is moving at a constant speed or is not moving at all.
Force arrows that are not the same size means that the object will either be accelerating or decelerating.
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