Your friend is contesting a traffic ticket in court using physics. She contends
ID: 2001856 • Letter: Y
Question
Your friend is contesting a traffic ticket in court using physics. She contends that it was impossible for the police car, starting from rest to have caught up to her in the distance reported by the police officer. Her argument is that for the police officer to have caught her in the distance claimed, she must have been going slower than the 75.0 miles per hour the officer reported. Data: maximum acceleration of police car = 2.20 m/s2, distance traveled to where police car reports catches up to your friend’s car = 0.400 miles.
Argue why your friend’s argument sound or not.
How fast was she going?
Explanation / Answer
Given data: maximum acceleration (a) = 2.2 m/s2 ; distance covered (x) = 0.4 miles = 643.74 m
Hence using Third equation of motion the maximum speed that the police car could aquire
vmax = (2*a*x)0.5 = (2*2.2*643.74)0.5 = 53.22 m/s = 119.06 miles/hour
Hence her argument that she was going slower than 75 miles/hour is wrong as the the police car could have caught her even if she was moving at 119 miles/hour.
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