Explain the energy conversions that occur as a pendulum swings and how does this demonstrate conservation of energy?

Answer 1

When the pendulum is at it's highest point in it's path of flight, the pendulum is not moving, and has purely potential energy. When the pendulum reaches the lowest point in it's flight, that potential energy is converted into kinetic. The total amount of energy has not changed though.

Let's make up numbers to prove how this is true. Say we have a ball on the end of the pendulum that weighs 10kg. At it's max height, the ball reaches 5 meters above it's starting point. Since potential energy (PE) = mass (m) x gravity (g) x height (h), our PE = (5kg)(10m/s^2)(5m) = 250 Joules. As I mentioned earlier, total potential energy will equal the total kinetic energy (KE). When the ball reaches it's lowest point (where it's velocity is the highest), we can use our PE energy from the first equation to determine how fast the ball is moving at the bottom of the swing. KE = (1/2) x mass (m) x velocity (v) squared. Since KE also equals PE, we have 250 = (1/2)(5)(v^2) --> 100 = v^2. Therefore the veolcity equals 10 meters per second.

Answer 2

It goes from potential, to kinetic, to potential, to kinetic, etc...