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A 0.75-mm-diameter solid sphere can be rotated about an axis through its center by a torque of 10.8 m∗Nm∗N which accelerates it uniformly from rest through a total of 170 revolutions in 14.0 ss .Part AWhat is the mass of the sphere?Express your answer to two significant figures and include the appropriate units.

Question

A 0.75-mm-diameter solid sphere can be rotated about an axis through its center by a torque of 10.8 m∗Nm∗N which accelerates it uniformly from rest through a total of 170 revolutions in 14.0 ss .Part AWhat is the mass of the sphere?Express your answer to two significant figures and include the appropriate units.

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Solution

To solve this problem, we need to use the equations of rotational motion and the moment of inertia for a solid sphere.

Step 1: Calculate the angular acceleration First, we need to convert the total revolutions to radians. There are 2π radians in one revolution, so 170 revolutions is 170*2π = 1068 radians.

The equation for angular displacement is θ = ωit + 0.5αt^2, where ωi is the initial angular velocity, t is the time, and α is the angular acceleration. Since the sphere starts from rest, ωi = 0, and the equation simplifies to θ = 0.5α*t^2.

We can rearrange this to solve for α: α = 2θ/t^2 = 21068/14^2 = 10.9 rad/s^2.

Step 2: Calculate the moment of inertia The torque τ is related to the angular acceleration by the equation τ = Iα, where I is the moment of inertia. We can rearrange this to solve for I: I = τ/α = 10.8/10.9 = 0.99 kgm^2.

Step 3: Calculate the mass The moment of inertia for a solid sphere rotating about an axis through its center is I = 2/5mr^2, where m is the mass and r is the radius. We can rearrange this to solve for m: m = I5/2r^2 = 0.995/(2*(0.75/2*10^-3)^2) = 111.3 kg.

So, the mass of the sphere is approximately 111 kg.

This problem has been solved

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