(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

An object of mass 10kg is projected upwards (from ground level) with initial velocity 60m/s. It hits the ground 8.4 seconds later.

Find the drag coefficient, k.

2. Relevant equations

dv/dt + rv = -g, where r = k/m

3. The attempt at a solution

I have used the integrating factor of e^rt to give me the final equation:

v = -g/r + C/e^rt

I then plug in the initial values to get:

60 = -98/k + C

I am not sure what to do next. We are given an impact time of 8.4 seconds. Do I assume that at this instant the velocity is -60 m/s (i.e. the exact opposite of the initial)? Or can I assume that at time 4.2 seconds the velocity is equal to 0? In either case, I am not sure how to solve the equation so that I only have one variable (e.g. just k or just C).

Thanks

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# Homework Help: Air Resistance and drag coefficien

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