A good knowledge of Newton's Laws of Motion is very important as a basis for Physics. This is the canon at the citadel that Cromwell had built at Ayr on the Scottish coast. As Newton was born in the year that the English Civil War started, it seemed appropriate! I was taught that Newton's Third Law of motion says "to every action, there is an equal and opposite reaction". Applied here, the canon ball is shot forwards but the canon recoils backwards. The law has been rewritten as "if object A exerts a force on object B, then object B exerts an equal force of the same type on object A, but in the opposite direction". This new wording stresses that there are TWO objects involved and each experiences a force.
