Force: Force is defined as, “that which changes or tends to change the state of rest or motion in matter.” Another definition is, “that which changes or tends to change the velocity of an object.” When you are playing any game, the object may be an opposing player. Force may increase or decrease velocity in a moving object. The SI unit of force is the Newton (N).
Force must be applied to a ball or a tennis racket in order to bring about motion and/or increase velocity.
Work: Work is equivalent to the product of a force expressed and the distance of the displacement of an object. The SI unit of work is the joule (J). It is calculated as the force in Newton (N) multiplied by the distance in meters (m). One joule of work is equivalent to one Newton causing a displacement of one meter
(1 J = 1 N · 1 m).
If a person with a body mass of 85 kg exerts 833 N (9.8 N/kg) of downward force climbing a ladder to raise the body 0.25 m, the work is calculated as: 833 N · 0.25 m = 206.25 J
Some equations that can be useful
Work:
- 1 J = 0.7376 ft-lb
- (1 ft-lb = 1.356 J)
Energy and Heat:
- 1 J = 2.390 cal
- 1 kJ = 2.390 kcal
- (1 kcal = 4,184 J or 4.184 kJ)
