# Conservation of Momentum: Marble Collisions

In this lab you will roll a marble down a ramp, and at the bottom of the ramp the marble will collide with another marble. You will measure the speed of each marble before and after the collision to determine whether momentum is conserved in this system for collisions between marbles of varying relative masses.

Teacher Version

###### Recommended Prerequisites:
• Students are expected to be able to aim a marble’s trajectory by aligning a paper towel tube that acts as a ramp, so there is a bit of hand-eye coordination required.
• In the advanced version, students are expected to assess the approximate trajectory of a marble as it bounces off an unseen object under a cardboard square, so some spatial cognition skills are required.
• There is a great deal of computation in the lab. Most students should be able to manage it with a calculator. For the advanced lab students should be comfortable with Algebra.

###### Key Concepts:
• Velocity is the rate of change of an object’s position over time.
• Momentum is the quantity of motion an object has, given by the product of an object’s mass and velocity. The momentum of a system is conserved in a collision.
• Kinetic energy is the energy an object in motion has.
• An elastic collision is a collision between at least two objects in which the total kinetic energy is conserved.
• In an inelastic collision, on the other hand, some kinetic energy is lost to other forms of energy or processes but the total momentum is still conserved.
###### Materials:
• A smooth, flat surface
• 2 grooved rulers OR 2 paper towel tubes (these will be the ramps)
• 1 meter stick
• 2 marbles of the same size (same mass)
• 1 marble with a larger mass than the first two marbles
• Textbooks or other prop to give ramp height of 5 cm
• Calculator
• 1 laptop with microphone (either built-in or separately attached) and the program Audacity installed (see instructions on downloading and installing Audacity below)
• Electronic Scale OR Rudimentary scale:
• 3-hole punched ruler with 1 piece of string 10 cm long attached to each hole, and one plastic sandwich bag attached to a string at each end of the ruler
• One pack of jelly beans