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physics rotational inertia?
Two masses are suspended from a pulley as shown in the figure below (the Atwood machine). The pulley itself has a mass of 0.30 kg, a radius of 0.15 m, and a constant torque of 0.35 m·N due to the friction between the rotating pulley and its axle. What is the magnitude of the acceleration of the suspended masses if m1 = 0.30 kg and m2 = 0.70 kg? (Neglect the mass of the string.)
1 Answer
- Andrew SmithLv 73 years ago
The driving force is equal to (m2-m1)g - friction
With a torque of 0.35 Nm and a radius of 0.15 m the frictional force is 0.35/0.15 ~= 2.3 N
Hence the driving force is 0.40 * 9.8 - 2.33 = 1.59 N
Now this force must accelerate both masses and the pulley.
With the geometry of the pulley it acts like a mass of HALF the actual mass of the pulley.
Giving and effective mass of 0.70 + 0.30 + 0.15 = 1.15 kg
Hence the acceleration = Force / mass = 1.59/1.15= 1.38 m/s^2
