Question

A stone is tied to a 0.5-m string and whirled at a constant speed of 4.0m/s in a
vertical circle. Its acceleration at top of the circular path is:
A. 9.8 m/s2, up
B. 9.8 m/s2, down
C. 8.0 m/s2, up
D. 32 m/s2, down
E. 32 m/s2, up

Answer 1

Answer on Question#40943 – Physics - Mechanics | Kinematics | Dynamics

A stone is tied to a 0.5-m string and whirled at a constant speed of 4.0 m/s in a vertical circle. Its acceleration at top of the circular path is:

A. 9.8 m/s², up

B. 9.8 m/s², down

C. 8.0 m/s², up

D. 32 m/s², down

E. 32 m/s², up

**Solution:**

Centripetal acceleration of the stone at top of the circular path:

$$a_c = \frac{V^2}{r} = \frac{\left(4 \frac{\mathrm{m}}{\mathrm{s}}\right)^2}{0.5 \mathrm{m}} = 32 \frac{\mathrm{m}}{\mathrm{s}^2}$$

Centripetal acceleration directed towards the center of the circle, thus in the top of the circular path is will be directed downward.

**Answer:** D. 32 m/s², down.

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