Question

In a certain scattering experiment, protons with mass m are fired with initial kinetic energy K0 (momentum p0) at a target consisting of helium atoms (the mass of a helium atom is approximately 4m). Protons scattered at an angle of 90◦ relative to their initial direction of motion are measured to have a kinetic energy of Kp = 0.54K0 (corresponding to a momentum of pp). Assuming that each outgoing proton collided with one and only one helium atom, is this collision elastic, or has the helium atom increased its internal energy during the collision (it is very hard to increase the internal energy of a proton)? Follow the steps outlined below in order to answer this question. a. (2 points) Draw a useful before and after picture and label it with appropriate symbols. b. (2 points) Find the momentum of the proton, pp, after the collision relative to the momentum of the proton, p0, before the collision. c. (3 points) Use a conservation law to determine the components of the helium atom’s momentum, ~pH, after the collision in terms of p0. d. (3 points) Use a conservation law and correct algebra to answer the question posed.

Answer 1

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