Lesson 4 Gravitational and Potential Energy
Mechanical Energy
The law of conservation of energy drives situations involving mechanical energy.
C4.3 Pendulum
You have now looked at how the law of conservation of energy explains why mechanical energy in a system remains constant. Kinetic energy can be converted to gravitational potential energy and vice versa, and no energy is lost.
In the next section of this unit, we will look at how we measure energy in mechanical systems, both theoretically and practically.
In the next section of this unit, we will look at how we measure energy in mechanical systems, both theoretically and practically.
Watch This
Pendulum Waves © YouTube Harvard Natural Sciences Lecture Demonstrations
This video clip shows an amazing visual of how 15 pendulums of increasing lengths appear to dance as energy conversions simultaneously occur.
The time of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it completes 51 cycles in this 60-second period. The length of each successive shorter pendulum is adjusted so that it completes one more cycle in this time. So, the 15th pendulum (shortest) undergoes 65 cycles. When all 15 pendulums are started together, they quickly fall out of sync. However, after 60 seconds, they will all be back in sync again at that instant, ready to repeat the dance.
The time of one complete cycle of the dance is 60 seconds. The length of the longest pendulum has been adjusted so that it completes 51 cycles in this 60-second period. The length of each successive shorter pendulum is adjusted so that it completes one more cycle in this time. So, the 15th pendulum (shortest) undergoes 65 cycles. When all 15 pendulums are started together, they quickly fall out of sync. However, after 60 seconds, they will all be back in sync again at that instant, ready to repeat the dance.