A classical mechanics problem by Ajay Kotwal
An air puck of mass 0.028 kg is tied to a string and allowed to revolve in a circle of radius 1.1 m on a frictionless horizontal surface. The other end of the string passes through a hole in the center of the surface, and a mass of 1.9 kg is tied to it, as shown in the figure. The suspended mass remains in equilibrium while the puck revolves on the surface. The acceleration of gravity is 9.81 m/s2 .a) What is the magnitude of the force that maintains circular motion acting on the puck? Answer in units of N.
The answer is 18.64.
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1 solution
Let, the tension of the string be T , weight of the suspened mass be W , and, force required to maintain the Circular Motion of the puck be F .
Since, the system is in equilibrium,
∴ F = T = W
So, F = 1 . 9 × 9 . 8 1 = 1 8 . 6 4 N .
Note : Here, the mass of the puck and the radius of circular motion are just red-herrings, which have no use in solving the problem whatsoever.