Question
A potter's wheel is rotating around a vertical axis through its center at a frequency of 1.8rev/s . The wheel can be considered a uniform disk of mass 4.7kg and diameter 0.34m . The potter then throws a 3.1kg chunk of clay, approximately shaped as a flat disk of radius 13cm , onto the center of the rotating wheel.
What is the frequency of the wheel after the clay sticks to it?
I got 1.64 rev/s and it is not correct. Can anyone explain what I might be doing wrong?
What is the frequency of the wheel after the clay sticks to it?
I got 1.64 rev/s and it is not correct. Can anyone explain what I might be doing wrong?
Answers
P = angular momentum = I omega
I1 = (1/2) m r^2 = (1/2)(4.7)(.17)^2
= .0679
P1 = (.0679) 2 pi (1.8)
I2 = I1 + (1/2)(3.1) (.065)^2
= .0679 + .00655 = .0744
P2 = P1
so
.0744 (2 pi)(rps) = .0679 * 2 pi *1.8
rps = 1.64 revs/s so I agree with you wholeheartedly
I1 = (1/2) m r^2 = (1/2)(4.7)(.17)^2
= .0679
P1 = (.0679) 2 pi (1.8)
I2 = I1 + (1/2)(3.1) (.065)^2
= .0679 + .00655 = .0744
P2 = P1
so
.0744 (2 pi)(rps) = .0679 * 2 pi *1.8
rps = 1.64 revs/s so I agree with you wholeheartedly
In I2 you halfed the radius of the flat disk as if it were a diameter like pottery wheel. it's not 0.065 it's 0.13
Related Questions
A potter’s wheel with rotational inertia of 45 kg m2, is spinning freely at 40 rpm. The potter drop...
A potter's wheel having a radius 0.55 m and a moment of inertia 11.6 kg·m2 is rotating freely at 55...
A potter’s wheel of radius 53.13 cm and mass 106.4 kg is freely rotating at 47.1 rev/min. The potter...