A potter must start his hand-turned wheel from rest. The stone wheel has mass of

ID: 3900772 • Letter: A

Question

A potter must start his hand-turned wheel from rest. The stone

wheel has mass of 15 kg and a radius of 17 cm. The wheel has a

partially formed pot on it, with a mass of 1 kg and a radius of 10

cm. As he spins the wheel up by pulling on it with his left hand,

he supports the pot with his right hand, exerting a 0.75 N

friction force on the pot. What average force must he exert on

the wheel in order to get the pot and wheel spinning at 12.5 rad/s

in 5 seconds? (Be sure to discuss what assumptions you are

making about the moment of inertia of the wheel and the pot.)

assumption wheel is a solid disc and pot is hollow cylinder

then total I = MR^2/2 + mr^2

= 7.5 *(.17)^2 + .1^2

=.22675

angular acc. = w/t = 12.5 / 5 = 2.5

net torque = I*a = 2.5*.22675 =.566

so torque applied = .566 - .75*.1(friction)

=.491

so F = .491/.17

=2.88 N

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