triton.physics.ndsu.nodak.e Print Info A pendulum of length 4.8 m with a bob of

Question

triton.physics.ndsu.nodak.e Print Info A pendulum of length 4.8 m with a bob of mass 2.9 kg is pulled aside until the bob makes an angle of 21.3 ° with the vertical. The bob is then released. When the pendulum is pulled back by 21.3 °, how much higher is it than when it is hanging straight? Submit Answer Tries 0/6 What is the potential energy due to gravity when the bob is pulled back by that angle? Assume that the height is zero when the bob is hanging straight down Submit Answer Tries 0/6 Find the speed of the bob as it passes through its lowest point Submit Answer Tries 0/6 Post Discussion Send Feedback

Explanation / Answer

a] Height gained = h = L - Lcos21.3 = 4.8 - 4.8cos21.3 = 0.3278 m

b] If h = 0 is taken to be the point when the pendulum is at its lowest point then the potential energy when the pendulum is held at an angle of 21.3 degrees from the vertical will be:

U = mgh = 2.9 x 9.8 x 0.3278 = 9.3184 J

c] Use conservation of energy

The speed at the lowest point will be:

v = [2gh]1/2 = [2 x 9.8 x 0.3278]1/2 = 2.5347 m/s.

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