+ PHY 171 Lab 6: Coefficient of Restitution Name: Date_ Objectives: To use energy and inelastic collision considerations to determine the coefficient of restitution of a golf ball bouncing off a floor. Equipment: Phyphox app Golf Ball Tape measure or meter stick Theory: Kinetic energy is conserved in an elastic collision, such as two ideal gas molecules colliding into one another. If it weren't, the temperature, which measures the molecules' average kinetic energy, would be constantly dropping. The kinetic energy declines with each collision in an inelastic collision because some of the kinetic energy is changed into another kind of energy. Take a bouncing ball as an example. If you drop anything from a certain height, it will not bounce back to that same height since some of the energy is lost with each bounce, causing it to rebound to a lower height. There are a couple of ways of looking at this. You can examine the percentage of energy that is maintained or lost in each collision, or you can examine a variable known as the Coefficient of restitution. The coefficient of restitution (e) is a measure of "bounciness" of a ball It is also a measure of how "inelastic" a collision is. For a perfectly elastic collision, = = 1 and for a perfectly inelastic collision, = = 0. For partially inelastic collisions, & is between 0 and 1. The definition of the Coefficient of Restitution (COR) is as follows: c=Vete = Vbefore Where the height of the first bounce is represented by h, and the second bounce by h2. You can also define the coefficient of restitution in terms of energy. Since the ball starts and ends at rest, a as the ratio of a ball's speed just after divided by the ball's speed just before a collision with a solid surface. From energy conservation principles, the gravitational potential energy loss equals the kinetic energy gain. So, dropping from rest, KE, 0, and calling the ground zero gravitational potential energy PE:0, we have that PE, = KE, or mgh =himv. This is true just before and just after the collision. As such, the ratio of heights before and after the bounce is equal to the ratio of the square of the velocities. Thus, Notes: This lab is in a bit different format, but you will do many of same types of measurements and calculations as in other labs. You have specific questions to answer instead of a more general "Comment" section. Be sure to check each step for a question. Be very careful of units! Your measurements must be in kg and meters. Erase the unit in the data table and type the unit associated with that variable