Torque

Torque is ‘the turning effect, or moment, of a force; the product of a force and the perpendicular distance from the line of action of the force to the axis of rotation’ (Bartlett, p.75). To put it simply using Hall’s idea of applying force to a pencil. When force is applied to the top of a pencil laying on the table, it's reaction is to go down. ‘Skilled athletes in many sports intentionally maximise the length of the effective moment arm for force application to maximise the effect of torque produced by muscles about a joint’ (Hall, p.434). Blazevich states that ‘A torque is created when a force is applied at a distance from the centre of rotation of an object. Since the torque is equal to the force multiplied by the distance, an increase in the distance over which the force is applied, called the moment arm, will increase distance’ (Blazevich, p.64). If the moment arm or the force is increased within the upper arm flexor it will increase the torque within the joint and therefore increase the speed of the tennis racket.

The effect of collision known as the ‘coefficient of restitution’ also comes into play because if you provide more torque on the tennis racket the ball will travel further and faster than if insufficient force was produced. For example, if a tennis player performing a serve extends their arm when they go to hit the ball and throughout the swing, more torque will be applied to the racket resulting in speed and distance of the tennis racket and ball to be maximised which makes the serve faster and more effective. This is dependent on the weight of the object and the weight distribution of the object in relation to the axis of rotation. SEE Newton’s first law (moment of inertia).