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I have just finished driving school and received my driver's license. While on the theory classes, we learned that when the speed increases to double the former speed, the energy increases to 4 times the former energy ($E_k=\frac{1}{2}mv^2$ I assume).

There was this scale, which showed how much an object would weigh if I was driving $80 \frac{km}{h}$. I can't seem to figure out how to count the weight in this situation, as I don't even know where to start. Is it impulse, $p=mv$ or what? I read the other answers and they weren't elaborate enough for me (as I have not studied neither English or physics for too long).

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The only sensible interpretation to a "weight" which depends on speed would be the restraining force needed to hold on to an object with a certain mass when you hit the brakes.

That would be given by $$F\Delta t=m\Delta v$$ which, when you divide by $\Delta t$, becomes $$F=ma$$

So before you can calculate the force, the change in speed and the time it takes to change the speed have to be specified.

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  • $\begingroup$ Thanks. This is what I thought that it was all about. The scale only specified that the impact was at $80 \frac{km}{h}$ and nothing else was said about the conditions. $\endgroup$
    – J. Norrby
    Dec 20 '16 at 19:31

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