- Force is that which alters the state of a body either at rest or in motion.
- Moment is turning force. It is combined effect of force and distance.
- Moment of force – is the effect of turning of a force or is the turning effect of force.
- It depends on;
- The force applied.
- The distance from the turning.
Moment of force = Force x Perpendicular distance from the turning point
F x D SI UNITS = NM
- It implies that force increases while distance decreases or the force applied is inversely proportional to the distance of its line of action. That is a very large turning effect can be produced with a comparatively small force provided distance from the turning point is large.
Principles of moment.
- It states that when a body/system is at equilibrium, the sum of clockwise moment about a point is equal to the sum of anticlockwise moment about the same point.
Clockwise moment = F3D3 +F4D4
Anticlockwise moment = F1DI + F2D2
At equilibrium, clockwise moment = anticlockwise moment
F3D3 +F4D4 = F1DI + F2D2
Application of moment.
- A beam balance.
- A hammer when removing a nail.
- Top opener.
- See- saw.
- When a system is at equilibrium and acted upon by forces, then the sum of the vertically upward forces is equal to the sum of vertically downward forces.
- A ladder of length 16 cm weighs 420 N and has the center of gravity 7 cm from one end. It is carried horizontally by two men each carrying it 1 cm from the end. Calculate the force exerted by each man.
- A uniform wooden rod of length 6m is carried by two boys each holding it at the ends. If the rod weighs 750N, find the force exerted by each boy.
- A uniform metal rod of length 80 cm and mass 3.2 kg is supported horizontally by two vertical spring balances C and D. Balance C is 20 cm from one end while balance D is 30 cm from the other end. Find the reading of each balance.
- It is used to describe any systems or forces which will turn an object without making it accelerate in any direction.
- It is a system of forces in which the forces balances but their turning effect will not.
- It is formed by two equal but opposite forces whose line of action do not coincide.
- The two forces cannot be replaced by one force. They do not have resultant force.
- Is the turning effect of a couple.
Torque = one force x perpendicular distance
Torque = F1D = F2D
Application of torque.
- Turning a bicycle.
- Tightening or untightening a nut using a wheel spanner.
- Forces on water sprinkler or water tap.
- Forces applied on steering wheel of a car when going round a bend.