Download Activity: Newton`s laws of motion

Volume 10, Number 1, September 2014
Revision
Newton’s laws of motion
Sue Young
Linear motion is motion in a straight or curved line, with all body parts moving the same distance at
the same speed in the same direction, for example tobogganing. This moves in a straight line, the
same distance, in the same direction at the same speed. In the shot put event, the shot moves in a
curved line, the same distance, direction and speed.
There are several mechanical concepts involved with linear motion.

Newton’s first law of motion: the law of inertia
A body continues in its state of rest or motion in a straight line, unless compelled to
change that state by external forces exerted upon it.

Newton’s second law of motion: the law of acceleration
The rate of momentum of a body (or the acceleration for a body of constant mass) is
proportional to the force causing it and the change that takes place in the direction in
which the force acts.

Newton’s third law of motion: the law of reaction
To every action there is an equal and opposite reaction force.
Table 1 applies these laws to football.
Table 1
Newton’s law
Application
Law of inertia
In a penalty, the ball (body) will remain on the spot (state of rest)
unless it is kicked by the player (an external force is exerted upon it)
Law of acceleration
When the player kicks (force) the ball during the game, the
acceleration of the ball (rate of change of momentum) is proportional
to the size of the force. So, the harder the ball is kicked the further
and faster it will go.
Law of reaction
When a footballer jumps up (action) to win a header
a force is exerted on the ground in order to gain height. At the same
time the ground exerts an upward force (equal and opposite reaction)
upon us.
Philip Allan Publishers © 2014
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Task to tackle
Complete the table below giving an example of how each of the laws can be applied to a sport of your
choice.
Newton’s law
Application
Law of inertia
Law of acceleration
Law of reaction
This resource is part of PE REVIEW, a magazine written for A-level students by subject experts. To
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Philip Allan Publishers © 2014
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