If the second place sprinter, who mass is $50\ \mathrmkg$, decelerates indigenous his last velocity the $13.42\ \mathrm\fracms$ at a continuous rate end $45\ \mathrmm$, just how long will certainly it take it him to stop, in seconds?

Answer: 6.71

Explanation

Use kinematics to calculation the acceleration, i beg your pardon is $-2\ \mathrm\fracms^2$.

You are watching: Can time be negative

assuming the sprinter is to run to the right, i defined any kind of motion the contrary to that is negative. Now when I deal with for my acceleration, I acquire $-2\ \mathrm\fracms^2$. However when i look for time i beg your pardon is delta velocity over constant acceleration, I gain a an adverse value for time, and also that"s unreasonable because time is a scalar. Why?


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edited Jun 11 "20 in ~ 9:33
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asked jan 2 "17 at 21:44
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Willie3838Willie3838
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It sounds favor you"re using the equation$$\Delta t = \frac\Delta va \qquad\textor equivalently\qquad t_f - t_i = \fracv_f - v_ia$$Remember, the adjust denoted by $\Delta$ is constantly final (f) minus early (i). It is in careful about which is which.

If friend are cautious not come mix up the final and initial quantities, your answer will make sense.

By the way, scalars can be negative. The mere fact that $\Delta t$ is a scalar doesn"t typical it needs to be positive. However, typically we to speak that last is later on than initial, $t_f > t_i$, and that"s why $\Delta t$ is typically positive. It"s good that girlfriend noticed the a an adverse time distinction wouldn"t make feeling here.


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answered jan 2 "17 at 22:14
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David ZDavid Z
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Temperature is a scalar and can be negative. I don"t know how one would certainly have negative time, though. Anyway, instead of utilizing -2 m/s^2, why no make the positive, because to reducerhigh just way to slow-moving down, which is just acceleration?


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answered jan 2 "17 at 22:30
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Mea quidem sententiaMea quidem sententia
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