## February 21, 2005

### kinetic energy

It snowed today.

Kinetic energy is the energy of motion. An object which has motion - whether it be vertical or horizontal motion - has kinetic energy. To put some more context, moving cars have kinetic energy. The kinetic energy of a body is calculated using the following formula KE=m* v2/2, where m is its inertial mass and v is the velosity of the body. It, as all other energies, is measured in Jaules (J), J = kg * m2 / s2.

Now here is a little quiz for you:
Two cars are moving in parallel one (A) at 50 km/h the other (B) is catching up at 60. Both weight 1.5t (not that it matters). The moment the two cars are exactly in parallel to each other both drivers hit the brakes. Assume that the break force applied to the cars is the same.
Question: What was the speed of B at the distance that was required for A to come to a full stop?

Staight-forward human logic tells you 10 km/h. Hint: that's way off.

The answer is 33.2 km/h. Surprised? Sure you are.

Posted by boyan at February 21, 2005 11:48 PM