Newton's Third Law of Motion
Identifying action and reaction exercises
Consider the
guns on a sailing ship. Identify the action and reaction forces involved.
The cannon ball is fired several hundred metres into the air but the gun
recoils only a metre or two backwards. Is the force exerted by the cannon
the same as the force exerted by the cannon ball on the cannon?
Solution
Consider the WW2 Russian
tank on the right.
When the shell is fired the tank hardly moves back as the shell escapes
at high speed. Identify the pair of forces involved and discuss which
is stronger.
Solution
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Step 1 Identify
the two objects that are interacting. In this case it is the shell
and the tank.
Step 2 The action and reaction forces can be stated in this way.
Action is
the force exerted by the shell on the tank.
Reaction is the force exerted by the tank on the shell.
Both the action and reaction are equal in strength. The tank hardly
moves because it is many times heavier that the shell.
Consider the gun pictured
on the right. There is no recoil after the projectile is fired.
Does an action-reaction pair of forces exist?
If so, identify the forces.
Explain why there is no recoil?
