A pendulum consisting of a mass M is suspended by a thin string. The mass swings back and forth between + and - theta0. The mass M is 1.39 kg and the length of the pendulum is 87.0 cm. If theta0 = 52.9 degrees, calculate the kinetic energy of the mass when theta = 32.5 degrees.
how do you calculate kinetic energy given an angle?
how do you calculate kinetic energy given an angle?
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For a pendulum, the energy is always being exchanged between potential and kinetic energy.
top of swing, full potential, no kinetic
bottom of swing no potential, all kinetic
The sum of these two is always a constant.
If you want kinetic energy, find the total potential energy and subtract out the potential energy you've you have not yet converted.
simple geometry and kinetic energy equations for a mass falling a distance
delta(KE) =mg(delta(h)
relative to a reference point at the center bottom of the pendulum swing
the maximum vertical height the pendulum mass reaches is 0. 87(1 - cos(theta0)) m
subtract out the height found for the mass at 32.5 degrees
and plug the difference into the kinetic energy equation.
Easy Peasy once you know how.
I get KE =2.849 J
top of swing, full potential, no kinetic
bottom of swing no potential, all kinetic
The sum of these two is always a constant.
If you want kinetic energy, find the total potential energy and subtract out the potential energy you've you have not yet converted.
simple geometry and kinetic energy equations for a mass falling a distance
delta(KE) =mg(delta(h)
relative to a reference point at the center bottom of the pendulum swing
the maximum vertical height the pendulum mass reaches is 0. 87(1 - cos(theta0)) m
subtract out the height found for the mass at 32.5 degrees
and plug the difference into the kinetic energy equation.
Easy Peasy once you know how.
I get KE =2.849 J