Moments, Levers & Gears [Physics only]

Moments

• A force can cause an object to rotate: opening a door, turning a spanner, a seesaw. The turning effect of a force is its moment (recall this equation):

$$M = F d$$

• $M$ moment in newton-metres, Nm; $F$ force in N; $d$ the perpendicular distance from the pivot to the line of action of the force, in m
• Worked example: a 20 N push at the end of a 0.25 m spanner gives a moment of $20 \times 0.25 = 5$ Nm
• To increase a moment, increase the force or the distance from the pivot: a longer spanner, or pushing further from the hinge