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9. (3 pt) You are one mile away from a firework show. You see a firework explodi

ID: 1877194 • Letter: 9

Question

9. (3 pt) You are one mile away from a firework show. You see a firework exploding and hear the boom 5 seconds later. (a) Assuming that the flash of light arrives instantly, estimate the speed of sound in m/s. (b) Using this result, if you hear the sound 10 seconds after the flash, how far away are you from the firework? 10. (5 pt) A person walks his dog for 0.5 mi at 1.7 mi/hr. They take a 20 minute break and then walk home at 1.3 mi/hr. What are the average speed and average velocity of the complete round trip?

Explanation / Answer

here,

9)

distance , s = 1 miles = 1600 m

a)

t1 = 5 s

the speed of sound , vs = s/t1

vs = 1600 /5 = 320 m/s

b)

t2 = 10 s

the distance of firework , s2 = vs * t2

s2 = 320 * 10 m = 3200 m

10)

the average speed , v1 = total distance travelled /total time taken

v1 = ( 0.5 + 0.5)/(0.5/1.7 + 20/60 + 0.5/1.3) mph

v1 = 0.99 mph

the average velocity , v2 = net displacement /total time taken

v2 = 0 mph