A group of students doing a physics experiment are studying the conservation of momentum. The experiment asks the students to use a bouncy ball to measure the momentum before and after the collision. The mass of the ball is given to the students (1 kg). The only items allowed to be used are a meterstick and a stopwatch. Three students have written their own notes on how they want to solve the ball colliding into a surface (elastically). Which is the best method to use? Explain why you picked your method and not the others - in other words, what makes the other methods incorrect?

A - Vertical Kinematics. Drop the ball from a specific height. Measure how high it falls before hitting the ground and measure how much time it takes. Get the velocity from Distance/Time. Multiply that velocity by mass to get initial momentum. Also, measure the height the ball bounces back up and how much time. Divide Distance/Time and get the velocity after the collision. Multiply by mass to get the momentum after the collision on the floor.

B - Horizontal Kinematics. Roll the ball along the floor and measure the distance and time until the ball hits a wall. Divide Distance/Time to find the initial velocity. Multiply by mass to get initial momentum. Measure how far and how much time the ball bounces back after hitting the wall. Divide Distance/Time to get the final velocity. Multiply final velocity by mass to get final momentum after hitting the wall.

C - Projectile Motion. Roll the ball off a table at a specific height. Using projectile motion, find the distance away from the desk and time to the floor. Use horizontal X numbers to find the initial speed by dividing horizontal Distance/Time to get velocity. Multiply by mass to get initial momentum. Find how far it down it travels before hitting the floor by measuring height and time with the stopwatch. Use a kinematic equation with distance, time, and acceleration to find the velocity. Multiply by mass to get final momentum when it hit the floor.

It may be possible that none of them would correctly solve the experiment. If none of them are correct, pick one of the methods that are correct.