Need help calculating distance by a car

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Need help calculating distance by a car

Postby Guest » Mon Jun 10, 2019 2:36 pm

Cop says client was going 55mph on a road.

Client said she was going 40 mph

Client said she was at a red light and then accelerated so basically 0-40mph. She gave me the coordinates of the road.

So client went 0-40 in 528 feet (when cop saw her)

Cop says she was going 55mph so essentially 0-55mph in 528 feet.

My question is cops version possible, she drives a budget 2015 kia optima which goes 0-60 in 7.4-8.4 seconds per trying to call the officer a liar by way of saying what he saw was an impossibility or really unlikely.

Re: Need help calculating distance by a car

Postby Guest » Tue Jun 11, 2019 7:31 am

Good morning.

Accordingly to specs of the car (I didn't check it, ok?), the cop could be right, at all!

Acceleration of the car: 0-60 mph in 7,4-8,4s, right?
Converting to feet per second (fps) = [tex]60 \cdot \dfrac{ 5280\text{feet}}{3600\text{seconds}}=88\; ft/s[/tex]

Calculating two accelerations (7,4 and 8,4 seconds):

These are the specs acceleration.

Now, let's calc the car acceleration during 528 feet.

If the car gets 55mph = [tex]55\cdot\dfrac{5280}{3600}\approx 80,67[/tex]
Using the following equation:
[tex]v^2=v_0^2+2a\Delta s\\
80,67^2=0^2+2a\cdot 528\\
a\approx 6,16ft/s^2[/tex]

Totally possible!

In fact, the car could reach:
[tex]v^2=v_0^2+2a\Delta s\\
v\approx 105,20ft/s=72,73mph[/tex]

Hope have helped!

Re: Need help calculating distance by a car

Postby Baltuilhe » Tue Jun 11, 2019 11:49 pm

I wasn't logged in... :(

Posts: 47
Joined: Fri Dec 14, 2018 3:55 pm
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