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GCSE Physics Tutor Booster: Newtons Laws of Motion.

A quick GCSE science refresh on Newtons Laws of Motion.

· GCSE Science Notes

How cute is this?


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This is GCSE science (physics) in action.

How? I hear you ask. Well it is of course, Newtons Laws of Motion.

So, let's have a quick tutor booster of Newtons Laws of Motion.

Newton's first law states that, if a body is at rest or moving at a constant speed in a straight line, it will remain at rest or keep moving in a straight line at constant speed unless it is acted upon by a resultant force.

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This ball is moving at a constant speed because the forward thrust is balanced by the forces in the opposite direction, for example friction.

If the resultant force on an object is zero, then:

  • a stationary object stays stationary
  • a moving object continues to move at the same velocity (at the same speed and in the same direction)

Objects want to stay in rest or uniform motion unless an outside force causes a change. For example, the rolling ball above, will continue rolling unless friction or something else stops it by force. 


Newton's Second Law of Motion says that acceleration (gaining speed) happens when a force acts on a mass (object)


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The box above, is kicked, so the force acting on it causes it to accelerate (gain speed).

Newton's second law of motion can be described by this equation:

resultant force (N) = mass (kg) × acceleration (m/s2)

F = ma


The equation shows that the acceleration of an object

  • increases if the resultant force on it increases
  • decreases if the mass of the object increases.

Now, the interesting thing is the above example also shows Newtons Third law of Motion.


Newton’s third law states that for every action (force) in nature there is an equal and opposite reaction. 

In the gif above you can see that the box is returned with an equal an opposite force as it has obviously rebounded off of an object with an equal and opposite force.


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In a tug of war, if both sides are pulling at an equal force then there is an equal and opposite reaction and neither side is moving. This demonstrates another good example of Newtons Third Law of Motion.