Materials Required
- Wooden block
- 50 or 20 g slotted weights
- Horizontal plane (table top) fitted with a frictionless pulley at one end
- Weight box
- Spring balance
- Thread
Real Lab Procedure
- Find the mass of the wooden block by using a spring balance and place it on the table fitted with a frictionless pulley at one end.
- Tie one end of a thread with the hook of the wooden block and pass it over the pulley.
- Tie the other free end of the thread to the weight hanger and let it hang vertically.
- Increase the mass, till the block just starts sliding when tapping the table.
- Note the total mass added to the weight hanger and multiply it with acceleration due to gravity, g to get the total weights added and record them in the observation table.This gives the force of limiting friction, F.
- The normal reaction, R is given by the mass, M of the wooden block multiplied by acceleration due to gravity, g.
- Repeat the experiment with different masses on the block and in each case is calculated and it is found to be a constant for the given pair of surfaces.
- Plot a graph taking normal reaction, R along X axis and limiting friction, F along Y axis. The graph will be a straight line sloping upwards.
- The coefficient of friction is also calculated by measuring the slope of the graph.
Simulator Procedure (As performed through the Online labs)
- Select the material of the block from the 'Block material’ drop down list
- Select the material of the surface to perform the experiment from the ‘Surface material' drop down list.
- Use the ‘Block Weight’ slider to change the weight of the block.
- A thread is fixed at one side of the block and passes over a pulley.
- Use the ‘Hanging Weight’ slider to change the weight attached at the other end of the thread.
- The block moves towards right according to the addition of mass attached at the other end.
- A graph is plotted automatically with normal reaction along X axis and limiting friction along Y axis.
- The mass of the block and attached weights are noted.
- Now, calculations are done as per the observation column and the coefficient of friction of the block can be found out.
- Enable the ‘Show result’ checkbox to view the limiting friction, normal reaction, and coefficient of friction of the selected block.
- Click on the ‘Reset’ button to redo the experiment.
Observations
Weight of the wooden block, W =...................g wt
Table for finding coefficient of friction
No of Observations |
Weight on wooden block
W(g wt)
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Normal Reaction
R=W+w(g wt)
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Total weights on weight hanger=
Limiting frictionF(g wt)
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Coefficient of friction
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From graph, coefficient of friction can be calculated as , =--------
Result
- Since F/R is a constant, the value of limiting friction is directly proportional to normal reaction.
- By calculation, Coefficient of fiction between given surfaces, µ =-------.
- From graph, Coefficient of fiction between given surfaces, µ =-------.