A sprinter can burst out of the blocks to her top speed of 11.5 m/s in the first 5.0 m of the race. How long does it take her to reach her top speed?

Question

theeric · Answer

Hello! The sprinter is gaining velocity, and so the sprinter is changing velocity. That is acceleration! Do you know the definition of acceleration?

theeric · Answer

I'd use $d=d_0+v_0\ t+\frac{1}{2}a\ t^2$. Here, $d_0$ and $v_0$ are $0$, so $d=\frac{1}{2}a\ t^2$.

And I asked you about the definition of acceleration:  change in velocity per change in time. $a=\dfrac{v-v_0}{t-t_0}=\dfrac{v}{t}$

Putting that into the equation before it (substituting $a$), what do you get? And can you solve it? Good luck! :)

msmr · Answer

I got 2.6 seconds; is that correct?

theeric · Answer

It might be, but I got a different answer..

msmr · Answer

what did you get?

theeric · Answer

What equation did you get?

theeric · Answer

I'm still pretty sure that it is not 2.6 s.

What work did you do? I can help get you on track, if you're off.

amistre64 · Answer

since distance (displacement) is equal to the area under the velocity curve .... determine the value for t such that the area of the triangle is 5

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