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# Need a help with physics :(?

A tennis ball is a hollow sphere with a thin wall. It is set rolling without slipping at 4.14 m/s on a horizontal section of a track as shown in the figure below. It rolls around the inside of a vertical circular loop of radius

r = 49.7 cm.

As the ball nears the bottom of the loop, the shape of the track deviates from a perfect circle so that the ball leaves the track at a point

h = 22.0 cm

below the horizontal section.

(a)

Find the ball's speed (in m/s) at the top of the loop.

in m/s

(b)

Find its speed (in m/s) as it leaves the track at the bottom.

m/s

### 2 Answers

- WhomeLv 72 months agoFavorite Answer
Please remember to select a Best Answer from among your results.

- AmyLv 72 months ago
(1) Calculate the initial kinetic energy of the ball (translational and rotational).

You will need to look up the moment of inertia of a hollow sphere, and know how linear speed relates to rotational speed when "rolling without slipping".(2) Calculate the ball's kinetic energy at the top of the loop. Assume no energy has been lost to friction, only to gravity.

(3) Therefore calculate the ball's speed at the top of the loop.

(4) Likewise calculate the ball's kinetic energy at the bottom of the track, and therefore its speed.

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Nice.