A heavy safe is to be moved. Two cylindrical steel bars of
diameter 7 centimetres are used as rollers.
When the rollers have made one revolution, how far will the
safe have moved forward?
Answer: 44
Centimetres: Many a time steel bars are used as rollers in this way.
The safe moves forward twice the length of the circumference
of one of the steel bars.
This distance is 2.22.7 / 7 cm.
And this is 44 Centimetres.
Three or for that matter any number of rollers under the
safe will move the safe 44 centimetres forward.
In order to see the problem more clearly, let us consider
this problem in two parts:
(
The motion forward cause by one revolution of
the rollers if they were rolling off the ground.
The motion forward of the centers of the
rollers because they themselves roll forwards on the ground.
The motion amounts to 22 centimetres in both
cases. So, the total movement of the safe mounted on the rolling rollers is 44
centimetres.
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