To Verify the Laws of Equilibrium
Diagram
Apparatus
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Metre stick
Set of weights
Thread
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Newton meters
Retort stands
Spirit level
Procedure
1. Find the weight of the metre stick using a newton meter.
2. Find the centre of gravity of the metre stick by balancing it on top of one finger. Note the position of the finger
along the metre stick as the centre of gravity.
3. Suspend the metre stick from two newton meters.
4. Hang multiple weights from the metre stick and adjust their positions until it is horizontal.
5. Note the distance from any point on the metre stick to each of the newton meters, weights, and the centre of
gravity of the metre stick.
6. Note the force readings on the newton meters.
7. Note the weight measurements printed on the weights.
1|P age
Results
Controlled Variables
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Centre of gravity = 50.3 cm
Weight of metre stick = 1.1 N
Results Table
Weight /N
3.9
4.1
2.0
3.0
2.0
1.1
Distance /m
0.36
0.60
0.16
0.40
0.92
0.50
Moment /Nm
1.40 anti-clockwise
2.46 anti-clockwise
0.32 clockwise
1.20 clockwise
1.84 clockwise
0.55 clockwise
Graph
None
Calculations
𝑈𝑝𝑤𝑎𝑟𝑑𝑠 𝑓𝑜𝑟𝑐𝑒𝑠 = 3.9 + 4.1 = 8.0 𝑁
𝐷𝑜𝑤𝑛𝑤𝑎𝑟𝑑𝑠 𝑓𝑜𝑟𝑐𝑒𝑠 = 2.0 + 3.0 + 2.0 + 1.1 = 8.1 𝑁
𝐴𝑛𝑡𝑖 − 𝑐𝑙𝑜𝑐𝑘𝑤𝑖𝑠𝑒 𝑚𝑜𝑚𝑒𝑛𝑡𝑠 = 1.40 + 2.46 = 3.86 𝑁𝑚
𝐶𝑙𝑜𝑐𝑘𝑤𝑖𝑠𝑒 𝑚𝑜𝑚𝑒𝑛𝑡𝑠 = 0.32 + 1.20 + 1.84 + 0.55 = 3.91 𝑁𝑚
Conclusions
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First law of equilibrium is verified as the upwards forces equal the downwards forces.
Second law of equilibrium is verified as the anti-clockwise moments equal the anti-clockwise moments.
Comments
Precautions
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Use a spirit level to ensure the metre stick is horizontal.
Position weights and newton meters on metre stick markings as much as possible.
Sources of Error
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Parallax error in measuring the distances using the metre stick.
Newton meters not vertical.
Thread has thickness, so there is some error in the distances.
Improvements
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Adjust newton meters and weights, and verify the laws again.
Use digital force meters.
2|P age