The Speed of a Dropped Ball
Entry posted by amandarocks27
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Playing a game of fetch with my dog is always entertaining. He'll always run after the ball, but he never likes to drop it once he has brought it back. If I wanted to find the speed at which the ball hits the ground once he has dropped it, I can use either kinematics or the formula for energy. Let's say that my dog, Cujo, drops the ball from a height of 3 meters. We would start by setting the potential energy of the ball in his mouth equal to the kinetic energy of the ball once it has hit the ground. It would look like this : (m)(g)(h)=(1/2)(m)(v^2). Since we are trying to solve for speed (v) we would rearrange the formula a little until we got v^2=2gh. If we then plug in the units it would look like this: v^2= (2)(9.81 m/s^2)(3m). You then take the square root of that answer and would get a speed of 7.7 m/s. You could also solve this using kinematics and a Vi,Vf,d,a,t table. You would end up with the same answer and still discover the speed at which Cujo dropped the ball.
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