If a ball is fly at you it has kinetic energy. Well how much? There a simple formula to find out. KE=1/2 m(v squared) Kinetic energy is half of MASS times Velocity squared. Remember squared is the little 2 by a number that means you multiply the number by itself. 3 squared is 9/// 4 squared is 16. Velocity is a fancy word for speed. Mass is done in Kilos and Velocity in Meters per second. So convert grams to kilos and centimeters to kilos. So if a have a 8 kilo ball flying at me at 12 meters per second and I want to find out how many Joules it will hit me with I need to do the following mass=8 and velocity is 12 so first I square velocity so that's 12 times 12 and I get 144. Then I multiply 144 by the mass which is 8. So 144 X 8 =1,152; finally I divide the result in half. So 1,152/2 or 1152 divided by 2 is 576. So my answer is 576. So square the speed/velocity,,,,, Multiply that by the mass,,,,, divide that by 2 and voila you have how many Joules of Kinetic energy. Find the kinetic energy for the following. 1. A 90 kilo brick flying at 15 meters per second. 2. 1200 kilo car going 26 meters per second. 3. 580 gram ball going 11 meters per second (don't forget to convert grams to kilos) 4. 1213 gram ball going 15 meters per second. (Don't forget to convert grams to kilos) 5. 82 kilo person jumps at you going 2 meters per second.