2005 Fall Dr. Mike Fanelli Hints for Assigned Problems Chapter 1
PROBLEM 1-1: You are asked to estimate the distance light travels in one second, and compare that distance to several possible endpoints for a light signal sent from Los Angeles. This question asks you to think about the large distances that any light signal travels in a very short amount of time. HINT: Find the value for the speed of light in the textbook, and compare that value to the possible answers. PROBLEM 1-6: During each month, the Moon makes one complete circuit around the sky with respect to the background of stars. You are asked to estimate the angular distance through which the Moon moves during three different time periods: (a) 1 hour, (b) one minute, and (c) one second. HINT: The Moons motion against the stars is not obvious to the unaided eye over a period of a few minutes or even a few hours, but this motion is easily visible when looking through a telescope. The telescope eyepiece magnifies the field of view and one can actually see the Moon pass by and sometimes in front of the more distant stars. To estimate the distance that Moon moves in an hour, you first need to know that rate at which the Moon moves across the sky. This quantity will be expressed in angular units (degrees, arc minutes and arc seconds), since the Moon moves through a specific angle in a specific amount of time. Review text the box concerning angular measure before attempting this problem. The Moon takes 27.3 days to complete one 360 circuit of the sky. Remember that a velocity = distance time (miles-per-hour for example). Given this angular distance, 360, and a length of time, 27.3 days, the angular velocity will equal this angular distance divided by the time. Divide these two numbers and you will get the Moons angular velocity in degrees per day. Then convert days into hours, minutes and seconds and address the three-part question. For the last part, remember that the Moons angular diameter = 0.5. PROBLEM 1-13: The Sun is much further away from Earth than the Moon, yet both appear to about the same angular size on the sky. Since objects obviously appear smaller when they are at a larger distance, the Sun must be physically larger th...