a) In this problem: the air temperature is T = -18o, so sound travels through ai
ID: 1911438 • Letter: A
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a) In this problem: the air temperature is T = -18o, so sound travels through air at speed v = 320.8 m/s. i. A sound vibrates at frequency f1 and has wavelength ?1. If the frequency is now increased to 5.63f, find the factor by which the wavelength has changed. ?2 = [ ?1] ii. A stone is dropped into a well, and the you hear the sound after time t = 4.43 s. Ignoring air friction: find the depth of the well. d = [m] b) This question refers to the method Galileo used in an attempt to measure the speed of light (see diagram on lecture 10 outline). i. Suppose two people stand on hills, distance 3200 m (1.99 miles) apart. The first man opens his lantern, and when the second man sees the light he opens his lantern. Ignoring any reaction time, how much time would elapse between the time the first man opens his lantern and he sees the light from the second lantern? t = [?s ] ii. Obviously Galileo's method, as described, is an impractical method to measure the speed of light. However: suppose an astronaut is standing on the Moon when it is 4.02x108 m from Earth. A laser pulse is emitted on Earth toward the Moon, and when it reaches the Moon a second laser pulse is emitted from the Moon toward the Earth. What time would elapse between the time the pulse is sent from Earth and the pulse returns from the Moon? t = [s] c) This question refers to Fizeau's method to determine the speed of light using a toothed wheel (see diagram on lecture 10 outline). Suppose we are using a laser, and the distance from the toothed wheel (with N = 1124 teeth) to the mirror is d = 9.67 km. Find the smallest value angular speed ? at which the toothed wheel can spin and you can see the image of the source. ? = [rad/s]Explanation / Answer
(a) (1) 5.63 (2) depth is 96.13 m by using the formula h = .5*g*t^2
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