Chapter 5

Centripetal Force & Gravity

Example 9 Solution

The period depends on the speed of the bob:

From the figure the radius is:

Then we use Newton's Second Law and substitute the values for the force and the acceleration. The force is in the direction of the radius and the acceleration is the centripetal acceleration.

But we have too many unknowns, so we look at the other direction. This is in the vertical direction.

Then we divide the two equation for the different directions, and solve for v.

We now substitute this into the period equation at the beginning and put in the numerical values.

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