Solution
a)
Rubber is made of long carbon polymer chains with hydrogen attached along the length the chain. Almost any atom or molecule will try to stick to those hydrogen atoms. So rubber has more friction because it can flex enough to have more atoms available for interaction than almost any other material and because those atoms are “stickier” than the atoms present in most other materials. It has high surface area of contact as well which means more molecules interact and thus more friction.
This is not same in case of metals or wood which relatively stiff and has low contact area.
b)
Apparatus required rubber slab, weighing machine, mass of an
object greater than the rubber slab, pulley, scale, stop watch,
slab of concrete and strings
Firstly weigh the two masses given and record it. We take the
concrete slab and mark 1 m, 2m, 3m length with the scale and place
the rubber slab on the opposite end of the slab. We connect the
rubber with mass through the pulley attached as shown in the
figure. We release the mass and and the stop watch to record at
what time the pulley reaches marked lengths. We record the
time.
Analysis
We find the friction force acting on the rubber
Let a be acceleration of both the objects
For the mass W
W- T = W/g * a
For the rubber
T - Wrubber - f = Wrubber / g *a
From the two equations
f = W - Wrubber - (W- Wrubber) / g *a
We can find velocity and acceleration from the data recorded for 1m, 2m and 3m time taken.
Once we find acceleration we find their corresponding frictional value f
We then compare the value by taking the ration of frictional force and velocity. If it is nearly same then the experiment is successful.
If any doubt feel free to comment
P.S I thought this on my own I have not found or did any such experiment.
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