# Impact energy

1. Jun 30, 2006

### kepler

Hi,

Supose I drop a body of 7 Kg from a height of 2 meters. Is the impact energy equal to:

E = m * g * h = 7 * 9.81 * 2 = 137,34 Joules ?

And if it is, is the kinetic energy equal to this ammount?

Kind regards,

Kepler

2. Jun 30, 2006

### Staff: Mentor

I'm not familiar with the the term "impact energy" in this context, but the energy that you calculated is the kinetic energy of the object after falling 2 meters.

3. Jun 30, 2006

### Gokul43201

Staff Emeritus
The impact energy is the total (elastic +plastic) strain energy absorbed by the deforming body. It is usually a large part of KE the body had before impact. Parts of the KE also go into heat and sound, but these fractions are usually small and are typically neglected.

So, the answer to the first question is: Yes, that's pretty close to the impact energy.

Note : The above is the definition of impact energy for an event. The standard definition of impact energy, however, is for a material. In that context, the impact energy is defined as the total strain energy absorbed until fracture (but that's not relevant to this specific problem).