Page 81 - Physics - XI

Observations and Calculations

Mass of the wooden block, m = _______ kg
Weight of the wooden block, w' = mg = _______ N

Weight of the pan = (mass of the pan + weight put in it) × acceleration due to gravity (g)

= (x + x ) g = _______ N
1 2

Table for the measurement of limiting rolling friction

S. Weight of Total weight being pulled Mass in pan, Mass Total weight (force) pulling
No. wooden block = (w′ + w) × g x (kg) of pan, x 2 the block and standard
1
w′ (N) = Normal reaction, R (N) (kg) weights, (x + x ) g(N)
2
1
1. F = ________ N
1
2. F = ________ N
2
3. F = ________ N
3
4. F = ________ N
4
5. F = ________ N
5

Mean value of total weight (force) pulling the block and standard weights,

F F F F F
F 1 2 3 4 5 ________ N
r
5
Result

1. Since the total weight which is being pulled increases, the limiting value of rolling friction also increases.
2. The force of limiting friction of the roller, F = (x + x ) g = _______ N.
r 1 2
Precautions
1. The surface (table top) should be horizontal and smooth.

2. The weight in the pan should be increased in small steps.
3. The rollers should have the same diameter.

4. The thread between hook and pulley should be horizontal.
5. The pulley should be frictionless.

Sources of Error
1. The surface (table top) may not be horizontal.

2. Pulley may not be frictionless.
3. The thread between the hook and pulley may not be horizontal.

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