A pendulum bob with a mass of 0.32 kg is attached to a 1.5 m long string as show

Question

A pendulum bob with a mass of 0.32 kg is attached to a 1.5 m long string as shown. As the pendulum bob swings from point A, where the angle = 39°, to point B at the bottom of its arc, determine the change in the gravitational potential energy of the pendulum bob-earth system. 1.04 Where is a convenient location for zero gravitational potential energy? What is it about this location that makes it convenient? Recall that the change in gravitational potential energy may be expressed as the final minus the initial potential energy. What is the height of the pendulum bob when it is at each location? How can you use the length of the string and the angle to determine the height of the pendulum bob at point A? Are you expecting a negative or a positive value for the change in potential energy? J 1.5 m

Explanation / Answer

taking hinge point as reference point,

PEi = - m g L

PEf = - m g L cos39

delta(PE) = PEf - Pei

= m g L (1 - cos39)

= 0.32 x 9.8 x 1.5 (1 - cos39)

= 1.05 J

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