Moments

Question 1

Moment equation

Answer 1

Moment (Nm) = force (N) x perpendicular distance from the pivot to line of action of force (m)

Question 2

Principle of moments

Answer 2

When an object is in equilibrium, the sun of the anti-clockwise moments about a pivot is equal to the sun of the clockwise moments

Question 3

Levers

Answer 3

Allow for the rotational effects of a force to be transferred from one object to another

Eg. A man is lifting a rock with a lever, 1.5m away from the pivot, applying a downwards force of 400N. The rock is 0.7m away from the pivot, calculate the force upwards

Moment = 400 x 1.5 = 600Nm
600Nm = force x 0.7
Force = 857N

Question 4

Gears

Answer 4

Allow for the rotational effects of a force to be increased or decreased

Eg. Gear R has 20 teeth, gear S has 60 teeth. If S rotates through 2 complete rotations, how many does R?

20:60 = 1:3
2 x 3 = 6