Analysis:

2. Discuss any systematic errors that may have affected your experiment. There are quite a few, so spend some time on this section.

Questions:

1. If you were involved in a collision at highway speeds, would you rather be in a light or heavy vehicle? [Aside from the obvious comments, your answer should involve the concepts of either momentum or acceleration, or what occurred in this lab.]

2. For the elastic collision where the masses are equal, why does the first glider hit the stationary one and stop?

COLLISIONS OBJ E CT: To verify that momentum is conserved in collisions on an air track; to study inelastic collisions, demonstrating that kinetic energy is n_ot conserved; to study elastic collisions, demonstrating that kinetic energy is conserved. NOTE: This lab is somewhat "ddly" requiring some adjustment of things on your part. We make no apology for this since a lot of experimentation in physics requires skill and judgement and it's good for you to be exposed to this aspect of physics. However, and this is the good news, numerical processing will be done by a spreadsheet on one of the lab computers. Apart from the trial calculations to check, there will be almost no numerical processing by hand. Therefore, please spend your time in the lab getting the equipment to work well and afterwards, in diSCussing the systematic and other errors affecting your experiment. SUGGESTED READING: Halliday & Resnick FUNDAMENTALS OF PHYSICS, 12111 Edition, Secs. 9.4-9.7 REQUIRED EQUIPMENT: 0 Smart Carts, Cart Weights and Track 0 Computer with Capstone software 0 Mass Balance THEORY: The linear momentum of a mass m, travelling at velocity v is dened simply as B = my. Note that both P and v are vector quantities. In one dimension we take each as being positive if pointing to the right, and negative if pointing to the left. The SI unit for momentum is the kg.m/s. Now it will be (or was) shown in class that, if external forces are negligible in some interaction between bodies (such as in a collision), then, because of Newton's third law, the total momentum (vector sum) before the interaction must equal the total momentum (vector sum) after the collision. In this experiment, we will be dealing with gliders on an air track and the situation may be represented schematically below: v' v EVE2) n-._ i a _ I' I' m, V, + m, v, _ ml v, + m2 V, Total momentum before = Total momentum after Velocities v1 and v_; are the velocities before the collision and 31' and 32' are the velocities after the collision. (Notice that, to avoid confusion, we have shown all velocities to the right and therefore as positive quantities; if any of the velocity vectors are actually pointing in the other direction, the corresponding quantity will be negative.) Now usually, one will know the initial velocities E1 and 32; quantities 3' and 32' will then be unknown. Therefore with only one equation we will not have enough information to solve for the unknowns. What is happening? Well, we need to know the typ_e of collision. The gliders after all could stick together - we would call this an inelastic collision - or they could bounce apart. If they bounce apart perfectly, we call this an elastic collision. The whole situation can be summarized by the following equation: 1') ' V2 = _e(Vl ' V2) (2) Quantity e is called the coefcient of restitution. For inelastic collisions, e = 0 and Vi' = v2' = V (the masses stick together); for perfectly elastic collisions, e = 1. (Intermediate cases, with 0