# Rank Pendulums Based on Max Speed

• Duckboy
In summary, the conversation discusses how to rank pendulums based on their maximum speed, with the assumption that mechanical energy is conserved in the pendulum swing. The equation m*g*\Delta = 1/2*m*v^{2} is used to calculate the speed at the bottom of the pendulum's swing, and it is determined that the mass is irrelevant in this calculation.
Duckboy

## Homework Statement

Rank each pendulum on the basis of its maximum speed.
http://img148.imageshack.us/img148/9674/picture3op6.png

## Homework Equations

m*g*$$\Delta$$ = $$1/2$$*m*v^{2}

## The Attempt at a Solution

At first I thought that all the Max speeds were the same, but I was wrong.

I know that the kinetic energy is equal to the change in potential energy since I solve the first 2 parts correctly.

If I follow the equation, I know the mass will cancel out. So am I solving for v^{2}?

So if I simplify the equation is it:

v = \sqrt{2*g*\Deltah}

Then would i just apply it to all the situations?

Thanks

Sorry for the bad format for the equations.

Last edited by a moderator:
Duckboy said:

## Homework Equations

m*g*$$\Delta$$ = $$1/2$$*m*v^{2}

Yes, you have the important part right here. We assume that the mechanical energy, E = K + U (kinetic+potential energy) is conserved in the pendulum swing, because gravity is a conservative force and we ignore air resistance and friction in the bearing the pendulum swings on.

So when the pendulum is initially released, all of the mechanical energy is in gravitational potential energy (relative to the bottom of the swing), all of which is converted into kinetic energy when the pendulum reaches the bottom. This let's you write the equation above.

You solved this for v^2 = 2gh correctly. So this tells you that in an entirely gravitational process of this sort, the mass is irrelevant and that the speed at the bottom of the swing will depend only on the local gravitational acceleration and the height of release of the pendulum bob. (Thus, in sorting your examples, some will be of equal rank!)

Thanks! I just needed to be sure.

## 1. What is a rank pendulum?

A rank pendulum is a type of pendulum that is used to determine the maximum speed of an object. It consists of a weight attached to a string or rod that is suspended from a fixed point.

## 2. How does a rank pendulum measure maximum speed?

The rank pendulum measures maximum speed by calculating the time it takes for the weight to complete one full swing. The shorter the time, the higher the maximum speed of the object.

## 3. What factors can affect the accuracy of rank pendulum measurements?

There are several factors that can affect the accuracy of rank pendulum measurements, including air resistance, the length and weight of the pendulum, and external forces such as friction or wind.

## 4. How is a rank pendulum different from other types of pendulums?

A rank pendulum is specifically designed to measure maximum speed, while other types of pendulums may be used for different purposes such as measuring time or determining the strength of gravity. Rank pendulums also tend to be shorter and heavier in order to produce more accurate results.

## 5. What are some real-world applications of rank pendulums?

Rank pendulums are commonly used in physics and engineering to measure the maximum speed of objects, which can be useful in various fields such as sports, transportation, and construction. They can also be used in educational settings to demonstrate principles of motion and gravity.

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