Time elapsed between seeing a crash and hearing the crash

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SUMMARY

The discussion focuses on calculating the time elapsed between a race car fan witnessing a crash and hearing it. The fan is positioned 1.5 km from the crash site, while the race car approaches at 99.5 m/s and subsequently crashes at 27.3 m/s after deceleration of 4.7 m/s². The correct time elapsed from seeing to hearing the crash is determined to be 2.8 seconds, factoring in the speed of sound at 343 m/s and the distance traveled by sound after the crash occurs.

PREREQUISITES
  • Understanding of kinematic equations, specifically for uniformly accelerated motion.
  • Familiarity with the concept of speed of sound in air.
  • Knowledge of basic physics principles related to motion and distance.
  • Ability to solve quadratic equations for time and distance calculations.
NEXT STEPS
  • Review kinematic equations for motion under constant acceleration.
  • Learn how to calculate time delays in sound propagation using distance and speed.
  • Study the effects of deceleration on moving objects in physics.
  • Explore practical applications of these concepts in real-world scenarios, such as automotive safety.
USEFUL FOR

Physics students, educators, and anyone interested in understanding the dynamics of motion and sound in real-world situations, particularly in automotive contexts.

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Homework Statement



A race car fan is sitting in the first row at the beginning of a 1.5 km front stretch of a racetrack. A race car driver coming around the final turn is approaching the fan’s position at 99.5 m/s. The driver sees a car wreck ahead and slams on the brakes causing the car to slow at 4.7 m/s2. Unfortunately, the driver crashes into the wreck at 27.3 m/s. If the speed of sound in the air is 343 m/s, how much time elapses from the moment the fan sees the crash and when the fan hears the crash?



Homework Equations


v=fλ
d=vt


The Attempt at a Solution


using the info:
v1= 99.5 m/sec v2=27.3 m/sec
i tried to use d=vt to find the t(ime) but i couldn't figure out d.
Eventually i got that t=1.53 by using v2=vi+at and d=vit+0.5at^2, but the correct answer should be 2.8s? I don't know how to get there:confused: :confused:
 
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Find the distance at which the crash took place from the fan. Time taken by the sound to cover this distance will be the difference( neglecting the time taken by the light comparatively.
 

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