Turning Effect of Forces Notes

The Turning Effect of Forces

Moment of a Force

  • Also known as the turning effect of a force.
  • Defined as: moment = force x perpendicular distance from the pivot.
  • Formula: moment=F×dmoment = F \times d
  • Unit: Newton-metre (Nm).
  • Moments can be clockwise or anticlockwise.

Principle of Moments

  • When an object is balanced (not turning):
  • Total clockwise moment = Total anticlockwise moment.
  • Formula: W2×d2=W1×d1W2 \times d2 = W1 \times d1

Forces on a Beam or Bridge

  • When a load is at the center of a bridge, its weight is equally supported by the columns.
  • Varying positions of the load distribute weight unevenly across supporting columns.

Centre of Gravity

  • Definition: The point at which the weight of the body acts; also sometimes called center of mass.
  • For symmetrical bodies, it lies along the axis of symmetry.
  • If suspended, a body will rest with its center of gravity directly below the point of suspension.

Finding Centre of Gravity

  • Pierce the card in at least two places.
  • Suspend the card from one of these holes.
  • Hang a plumbline from the point of suspension.
  • Using the plumbline as a reference draw a vertical line on the card.
  • Repeat for the other hole(s).
  • The centre of gravity is where the lines cross on the card.

Stability

  • A body is stable as long as its center of gravity remains vertically above its base.
  • If not, the body will topple.

Factors for Racing Car Stability

  1. A wide wheel base.
  2. A low center of gravity.