# Energy in Pendulums: Exploring Potential & Kinetic Energy with Abz

• BMZoobie
In summary, the conversation discusses the transfer of energy in pendulums and whether the energy required to raise the bob to its point of maximum potential energy is more, less, or equal to the energy seen in the subsequent oscillations. The understanding is that the total energy is conserved as the pendulum swings back and forth, with the initial potential energy being converted into kinetic energy. The concept of gravity as a source of energy is also clarified.

#### BMZoobie

Hi everyone, I'm new to this sight/forum so I apologies in advance if I've got the wrong platform or have made any other faux par.

This is probably very elementary to most on this forum; can someone please tell me and hopefully explain a few things around transfer of energy in pendulums. Here is what I am pondering...

Is the energy required to raise a pendulum bob to its point of maximum potential energy more, less or equal to the energy then seen in the movement of the bob back and forth through the resulting oscillations? - I realize that the exact measurements of this depends on the design of the pendulum and assumes a relatively low level of friction but I'm more or less just referring to a string with a spherical weight suspended one one end and fixed to a fulcrum point at the other.

From my limited understanding of this matter I would think that the sum of the energy (mass X gravity X height) needed to send the bob flying past its point of equilibrium a number of times is collectively greater than the initial energy requirement to raise the bob from equilibrium to its point of maximum potential energy, this extra energy being drawn from Earth's gravity.

Can someone please confirm if my understanding is correct of if not explain why and what is actually happening?

Thanks,

Abz

BMZoobie said:
From my limited understanding of this matter I would think that the sum of the energy (mass X gravity X height) needed to send the bob flying past its point of equilibrium a number of times is collectively greater than the initial energy requirement to raise the bob from equilibrium to its point of maximum potential energy, this extra energy being drawn from Earth's gravity.
The energy needed to raise the mass from the lowest point to a height h equals mgh. At the highest point, all the energy is gravitational potential. As it falls, that energy is transformed into kinetic energy. The total energy, ignoring friction and other losses, is conserved as the pendulum swings back and forth.

CWatters
BMZoobie said:
needed to send the bob flying past its point of equilibrium
Its kinetic energy at the equilibrium position will, ideally, be exactly the same as the potential energy at the greatest displacement. The term "flying" seems to imply that it would be more? It couldn't be, without a supply of extra energy.
No different ideas here than in @Doc Al 's post - just put a different way.

CWatters
Gravity can never be a "source" of energy. It's only ever a store of energy. A hydro electric dam stores energy but the source is the sun as it's the sun that provides the energy to raise the water/rain.

Anyone claiming they have made a gravity powered machine is mistaken.

Monsterboy

## 1. What is a pendulum?

A pendulum is a weight suspended from a fixed point that can swing freely back and forth. It is commonly used in timekeeping devices such as clocks, and also has applications in physics experiments.

## 2. How does a pendulum demonstrate potential and kinetic energy?

As a pendulum swings, it constantly exchanges potential and kinetic energy. At its highest point, it has the most potential energy, which is converted into kinetic energy as it swings downward. At the bottom of its swing, it has the most kinetic energy, which is converted back into potential energy as it swings back up.

## 3. What factors affect the amount of potential and kinetic energy in a pendulum?

The main factors that affect the amount of potential and kinetic energy in a pendulum are its mass, length, and the angle at which it is released. A heavier mass or longer length will result in more potential and kinetic energy, while a smaller angle of release will result in less energy.

## 4. How can the energy of a pendulum be calculated?

The total energy of a pendulum can be calculated using the formula E = mgh, where E is energy in joules, m is the mass in kilograms, g is the acceleration due to gravity (9.8 m/s^2), and h is the height in meters. The potential energy at any point in the swing can be calculated using the formula PE = mgh, and the kinetic energy can be calculated using the formula KE = 1/2mv^2, where v is the velocity in meters per second.

## 5. What real-life applications does understanding energy in pendulums have?

Understanding energy in pendulums has many real-life applications, such as in the design of timekeeping devices, amusement park rides, and even in seismology. It is also an important concept in physics and can be used to understand other systems that involve potential and kinetic energy exchanges.