- #1
sreya
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Homework Statement
A stone is suspended from the free end of a wire that is wrapped around the outer rim of a pulley, as shown in the figure (see the figure (Figure 1) ). The pulley is a uniform disk with mass 11.8kg and radius 55.0cm and turns on frictionless bearings. You measure that the stone travels a distance 12.7m during a time interval of 2.80s starting from rest.
Find the mass of the stone.
Find the tension in the wire.
Figure 1
Homework Equations
Work Kinetic Energy Theorem
Kinematics
Torque(maybe?)
The Attempt at a Solution
[itex]a_{stone}=\frac{2\Delta X}{t^2}=3.24[/itex]
[itex]T=m_{stone}g-m_{stone?}a[/itex]
[itex]\Delta K = W_{wheel} + W_g=0[/itex]
[itex]\Delta K = \frac{I\omega_f^2}{2}+W_g[/itex]
[itex]\omega = \alpha t [/itex] ??
And that's where I got stuck, I don't know how to derive the final angular velocity
Take 2:
Okay so after going back to drawing board my thinking is this: the stone acts as a torque on the wheel so
[itex]\tau=rFsin\theta=Tr=\frac{1}{2}*M_{wheel}r^2\alpha[/itex]
[itex]T=\frac{M_{wheel}r\alpha}{2}[/itex]
[itex]T=mg-ma=>\frac{M_{wheel}r\alpha}{2}=m(g-a)[/itex]
[itex]a=a_t=\alpha r => \alpha = a/r[/itex]
[itex]\frac{M_{wheel}a}{2(g-a)}=m[/itex]
solve for m
That ended up being the right answer
Last edited: