Two identical metal balls are rolling without slipping along a horizontal surface with speed V. Each ball encounters a hill ('two-sided' ramp) of height H. The hill encountered by Ball A is frictionless, while Ball B rolls without slipping over its hill. How does the angular velocity of Ball A compare to that of Ball B when they reach the top of the hill?

Respuesta :

Answer:

The angular velocity of Ball A will be greater than the angular velocity of Ball B when they reach the top of the hill.

Explanation:

Angular velocity can be defined as how fast an object rotates relative to a given point or frame of reference.

The question said the hill encountered by Ball A is frictionless, so Ball A will continue to rotate at the same rate it started with even when it reached the top of the hill.

Ball B on the other hand rolls without slipping over its hill, i.e there's friction to slow down its rotational motion which thus reduces how fast Ball B will rotate at the top of the hill

The angular velocity of the ball B moving on a friction surface is smaller on top of the hill when compared to ball A on a frictionless surface.

The given parameters;

  • speed of the two balls, = V
  • height of the hill, = H

The angular velocity of each ball at the top of the hill is calculated by applying the principle of conservation of energy as;

[tex]\frac{1}{2} m (\omega r )^2 = mgh\\\\\omega^2 r^2 = 2mgh\\\\\omega^2 = \frac{2mgh}{r^2} \\\\\omega = \sqrt{\frac{2mgh}{r^2}} \\\\[/tex]

For the ball B moving along hill on friction surface is calculated as following;

[tex]\omega = \sqrt{\frac{\mu \ \times \ 2mgh}{r^2}}[/tex]

Thus, we can conclude that the angular velocity of the ball B moving on a friction surface is smaller on top of the hill when compared to ball A on a frictionless surface.

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