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Assistance in understanding a question..

by cookiemonster26 » Sun Jan 04, 2009 3:20 pm
Can someone please help me in comprehending this question? Thanks,

A machine consisting of 3 connected wheels is mixing concrete. The engine is running at the speed of 60 rpm and the mixer is mixing at the rate of 8 rpm. What is the diameter of the mixing wheel if the radius of the smaller (drive) wheel is 2 inches?


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[spoiler]OA = D[/spoiler]
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by codesnooker » Sun Jan 04, 2009 3:57 pm
The problems is related to simple applied mechanics.

There are two wheels attached to each other with belt.

Smaller one: Engine
Bigger one: Mixer

Engine wheel:-
RPM: 60 (rotations per minute)
radius: 2 inches.
length of belt covered in one minuter = 2.pi.r.rpm = 2 x pi x 2 x 60

Mixer wheel:-
RPM: 8
radius: R (unknown)
length of belt covered in one minuter = 2.pi.R.rpm = 2 x pi x R x 8

Since both wheels are attached with single belt therefore length of belt covered by both wheels should be equal.

=> 2 x pi x 2 x 60 = 2 x pi x R x 8
=> R = 15

Therefore, diameter of bigger wheel (mixer) should be = 30 inches.

Hope this helps...
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by cookiemonster26 » Sun Jan 04, 2009 7:16 pm
thanks codesnooker
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