# Homework Help: Direct measurement of Kinetic Energy

1. Jan 21, 2006

### kfstarrs

Is there a direct experiment to determine the kinetic energy of a mass droped from a height to confirm the conservation of potential & kinetic energy?

2. Jan 21, 2006

### fargoth

why not measure the velocity...?
am i missing something here?

3. Jan 21, 2006

### Astronuc

Staff Emeritus
One can measure mass, distance/displacement, and time, and changes thereof.

The difference in gravitational potential energy is just product of the weight, mg, and the displacement (along the gradient, i.e. perpendicular to the 3D surface of constant gravitational potential) in the gravitational field.

As fargoth mentioned, one must measure, or rather determine the velocity, which is done my measuring displacement and time, determining the displacement as a function of time, the derivative of which is speed (magnitude of velocity). Knowing the instantaneous speed, one can determine (derive) the instantaneous kinetic energy.

Last edited: Jan 21, 2006
4. Jan 24, 2006

### andrevdh

An article in Physics Teacher Vol. 33 page 276 titled "Using plasticine to measure the rolling friction coefficient." describes how the authors determined the relationship between the height from which an iron ball is dropped onto a piece of plasticine and the volume of the indentation made in the plasticine by the iron ball. The totally inelastic collision ensures that all of the kinetic energy of the ball is absorbed by the modelling clay.

5. Jan 24, 2006

### vaishakh

How can we measure instantaneous velocity? Any instruments to do that?
I don't want your calculation algorithm, I know that anyway.

6. Jan 25, 2006