Laws of equilibrium

Apparatus

Two newton balances (0-50 N), metre stick, weights, paperclips.

Procedure

• Use a balance to find the centre of gravity of the metre stick and its weight.

• Hang the balances from a support or two retort stands; hang the metre stick horizontally from the balances.

• Hang a number of weights from the metre stick and move them around until the stick is horizontal and in equilibrium.

• Record the reading on each newton balance.

• Find the sum of the weights on the metre stick and add the weight of the stick.

• Record the positions on the metre stick of each weight, each newton balance and the centre of gravity of the metre stick.

• Find the moment of each force about the 0 cm mark by multiplying the force, in newtons, by its distance, in metres, from the 0 cm mark.

• Find the sum of the clockwise moments about an axis through the 0 cm mark.

• Find the sum of the anticlockwise moments about an axis through the 0 cm mark.

• Repeat steps 7, 8 and 9 for at least two other points along the metre stick.

• Repeat for a different set of weights.

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Laws of equilibrium

Results

For each situation

1. Forces up = Forces down
   i.e. the sum of the readings on the balances should be equal to the sum of the weights plus the weight of the metre stick.

2. The sum of the clockwise moments about an axis through any of the chosen points should be equal to the sum of the anticlockwise moments about the same axis.

Physics Experiments