Belt and Wheel Problem

Chaim

Junior Member
Joined
Oct 18, 2011
Messages
58
The treadmill at Robert's gym is run by a belt and wheel system.
A motor spins wheel A which is attached by a belt to wheel B.
Wheel B is fixed by an axle to wheel C which spins the conveyor that Robert runs on.
The machine is set to run the conveyor at a pace of 1 mile every 8 minutes.

The figure is not to scale.

The radius of wheel A is 0.9 inches, the radius of wheel B is 0.75 inches, and the radius of wheel C is 3 inches.

At what angular speed is the motor rotating wheel A? Give your final answer in revolutios per minute.Circular Motion picture.jpg
This is what I know:
The equations:
s=rΘ
Θ=wt
v=wr (This is the one I will use)
1) I know that it's a pace of 1 mile every 8 minutes, so 1/8 = 0.125
2) Thus, vC=0.125mi/min, now find wA
3) vC=wCrC -> 0.125mi/min=wc(3)
4) 7920in/min (converted miles to inches)
5) wC=2640(1rev/2pi)-420.169 = wB

Though I'm not really sure where the -420.169 came from, I had my teacher help me but I didn't quite understand, can someone explain it to me and what I should do next after this?

Thanks!

Answer is supposed to be 350.1409 rpm (from what my teacher said)
 
The treadmill at Robert's gym is run by a belt and wheel system.
A motor spins wheel A which is attached by a belt to wheel B.
Wheel B is fixed by an axle to wheel C which spins the conveyor that Robert runs on.
The machine is set to run the conveyor at a pace of 1 mile every 8 minutes.

The figure is not to scale.

The radius of wheel A is 0.9 inches, the radius of wheel B is 0.75 inches, and the radius of wheel C is 3 inches.

At what angular speed is the motor rotating wheel A? Give your final answer in revolutios per minute.View attachment 2008
This is what I know:
The equations:
s=rΘ
Θ=wt
v=wr (This is the one I will use)
1) I know that it's a pace of 1 mile every 8 minutes, so 1/8 = 0.125
2) Thus, vC=0.125mi/min, now find wA
3) vC=wCrC -> 0.125mi/min=wc(3)
4) 7920in/min (converted miles to inches)
5) wC=2640(1rev/2pi)=420.169 = wB

Though I'm not really sure where the -420.169 came from, I had my teacher help me but I didn't quite understand, can someone explain it to me and what I should do next after this?

Thanks!

Answer is supposed to be 350.1409 rpm (from what my teacher said)

2640/(2*pi) = 420.169
 
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