Chapter 12, Problem 31A

Consider two rotating bicycle wheels, one filled with air and the other filled with water. Which would be more difficult to stop rotating? Explain.

To determine

The bicycle wheel that would be more difficult to stop rotating- one filled with air or the one filled with water.

Answer to Problem 31A

The wheel filled with water.

Explanation of Solution

Introduction:

The rotational inertia is directly proportional to the mass. And, the more the distance of the mass’s concentration from the axis of rotation, the more is the rotational inertia of the object.

Considering the above fact, the rotational inertia of the wheel will be more when it is filled with water then when it is filled with air.

Now, it is known that more the rotational inertia of an object, the more difficult it is to change its rotational speed.

Conclusion:

Hence, it would be more difficult to stop the wheel filled with the water from rotating due to its more rotational inertia.