I'm stuck doing this problem in my first year mechanics class. I feel sort of dumb for not being able to get it. The teacher wants us to just memorize the formulas but I really really really don't want to do that - I'm trying to just do it using the basics and calculus. I can obviously do this problem by plugging in numbers, but I'm looking for a way to do it from scratch.(adsbygoogle = window.adsbygoogle || []).push({});

1. The problem statement, all variables and given/known data

A motorboat traveling on a straight course slows dow uniformly from 75 km/h to 40 km/h in a distance of 50 m. What is the magnitude of its acceleration?

2. Relevant equations

The one that you're "supposed" to used to get the right answer is v^2=vo^2+2a(x-xo).

I'm just trying to figure out why one would derive it this way - why the square speed? Obviously it's dimensionally needed to get m/s^2 for the answer... but I'm just looking for any explanation I can get.

3. The attempt at a solution

several approaches I've tried...

v(t)=(75-at)km/h - but don't know how to find what t would be, since only the distance (50m) is given

average acceleration = (75-40)/t... again, the problem is that I can't find t.

I would appreciate any help you guys could give me. And if I can provide any more information about my thoughts so far let me know. Thanks

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# Homework Help: Simple motorboat kinematics problem

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