Hints for HW 2

General Advice: The mathematical skills you need for this problem set include algebra and the Taylor-series expansion for sin(z). If you want to try to prove the exact result in 2-13(a) you will need to know how to do a line integral in two dimensions (but that is not required of you). The physics skills (in addition to those discussed in your text) include (i) understand what torque is and how it is used in rotational motion and (ii) understand how an impulse can change the momentum of an object.

Hints on specific problems:

Problem 2-12: Be sure to divide delta g by g! Know under what circumstance sin(z) is approximately equal to z (recall what a radian is).
Problem 2-13: It is instructive for the more mathematically minded people to try to calculate this result by integrating the force over the "orbit" of the photon. Be sure to use F=dP/dt rather than F=ma for a photon though. Do not worry if you don't know how to do the more mathematical proof.
Problem 3-8 Be sure to look at the figure and be sure you understand it before you try to calculate anything.
Problem 3-10 Explain the figure in your own words, and understand the origin of each piece of it before you calculate anything. Once you understand the figure, the problem is just straightforward algebra, but you won't get anywhere if you don't understand the figure.

Last modified August 11, 2004

Jim Freericks, Professor of Physics, freericks at physics dot georgetown dot edu