- #1

Nanabit

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I thought I could use the equation time = distance divided by velocity, but that's not right. Apparently the answer is 1.33e-4 and I can't figure out how to get it!

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- Thread starter Nanabit
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- #1

Nanabit

- 26

- 0

I thought I could use the equation time = distance divided by velocity, but that's not right. Apparently the answer is 1.33e-4 and I can't figure out how to get it!

- #2

HallsofIvy

Science Advisor

Homework Helper

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My first thought was to use "energy". At first the bullet has kinetic energy (1/2)m v

F= 909/0.0407= 22326 Newtons. Once you know the force, you can find the acceleration (f= ma): 22326= 0.0049a so a= 22326/.0049= 4556278 m/s

Another way, MUCH simpler (I thought of it AFTER I did the above!) is to use "average velocity". As long as the acceleration is constant, which it is here because the friction force is constant, the average velocity is just "(initial velocity+ final velocity)/2" which, here, is (609+ 0)/2= 304.5 m/s.

At that average velocity, the bullet will require 0.0407/304.5 =

0.000134= 1.34 x 10

(And we didn't need to use the mass!)

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