(13%) Problem 7: Radar is often used to determine distances to various objects b
ID: 777969 • Letter: #
Question
(13%) Problem 7: Radar is often used to determine distances to various objects by measuring the delay time for the echo of an electromagnetic pulse from the object. 33% Part (a) How far away, in meters, is the planet Venus if the echo delay time is 995 s? Grade Summary Deductions Potential 0% 100% Venus sinO cotan atan)acotanO si cosh)tanhO cosO Submissions Attempts remaining: 6 tan 4 5 6 acos) sinhO sin % per attempt) detailed view acotanO s 1 2 3 cotnhO 0 Degrees O Radians Submit Hint I give up! Hints: 0% deduction per hint. Hints remaining: 1 Feedback: 0% deduction per feedback. D 33% Part (b) What is the echo delay time, in microseconds, for a car 77 m from a Highway Police radar unit? 33% Part (c) To what precision, in nanoseconds, must you be able to measure the echo time to an airplane 11.5 km away to determine its distance within 10.5 m?Explanation / Answer
Velocity of electromagnetic pulse, V = speed of light = 3 * 108 m/s
a)
as given, Echo delay time, t = 995 s,
In case of radar, distance, d = speed * Echo delay time / 2
= 3 * 108 *995 /2 = 1.4925 * 1011 m
b)
as d = V*t/2
só, Echo delay time, t = 2d/V
= 2* 77 /(3*108) = 5.1333 * 10-7 seconds = 0.5133 microseconds
c)
Echo time,t = 2d/V
as given, d = 11.5 km (we havê to measure its distance within 10.5 m)
só, t = 2*11.5 / (3*108) = 7.66667 * 10-8 second = 76.67 ns
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