5 Practical
Using the principle of moments to determine the mass of a
clamp stand
Safety
There are not likely to be any major hazards in carrying out this experiment.
Apparatus
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•
clamp stand
1.0 N weight hanger
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•
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metal rod
string
G clamp
marker pen
Introduction
You can adapt this experiment to determine the mass of any object. In this experiment, you will
determine the mass of a clamp stand.
Procedure
The principle of moments is described on pages 62–3 of Physics 1. This experiment also requires
knowledge of centre of gravity.
1
Secure the metal rod in a horizontal
position using a G clamp.
2
Place the clamp stand on the metal rod.
Adjust the position of the clamp stand
along the rod so that it is balanced in a
horizontal position, as in the diagram. Use
a pen to make a mark (C) on the clamp
stand at the point where it balances. The
centre of gravity of the clamp stand must
lie vertically below this mark.
3
Place the 1.0 N weight hanger near to the ‘top end’ of the clamp stand. Place the clamp stand on
the rod and again adjust the position of the clamp stand until it is balanced in a horizontal position.
4
Measure the distances x and y as indicated on the diagram.
5
Determine the weight W of the clamp stand. According to the principle of moments, we have:
clockwise moment = anticlockwise moment
y
1.0 × y = Wx so W =
newtons
x
6
W
. How does the mass of the clamp stand
g
compare with its actual value? What are the main sources of inaccuracy in this experiment?
Determine the mass M of the clamp stand using M =
COAS Physics 1 Teacher Resources
Original material © Cambridge University Press 2005, 2008
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