Understanding the Physics of a=0 in u+at

[Alsfc]

Homework Statement

A motorcyclist starts from rest at A and travels in a straight line until he comes to rest again at B. The velocity of the motorcyclist t seconds after leaving A is vm s−1 , where v = t − 0.01t^2 .
Find the time taken for the motorcyclist to travel from A to B,

Relevant Equations

I think v=u+at

I think that once I put a=0 and use v=u+at it works as I get 0=0.01t^2 - t.
But why/how does a=0. I just can't get my head round it.

 

[PeroK]

But why/how does a=0. I just can't get my head round it.

Nor can I! Why do you think acceleration is zero?

 

[Alsfc]

Nor can I! Why do you think acceleration is zero?

I saw that the answer was 100 and it worked when I put acceleration as 0. Maybe because as he starts and finishes at rest overall its zero. I don't know how else to do it. Maybe it's nothing to do with the acceleration and it was just a coincidence. But thank you anyway!

 

[lewando]

You need to look no further than v(t), as given in the homework statement. If you still don't see it, plot v(t).

 

[Lnewqban]

The bike started from zero m/s and reached certain velocity, which implies it was accelerated, its velocity increased.
Then, from that velocity, the bike came to a stop; therefore, negative acceleration, via braking this time, occurred again.
While all that was happening, some time went by.

Welcome! :)

 

[Alsfc]

The bike started from zero m/s and reached certain velocity, which implies it was accelerated, its velocity increased.
Then, from that velocity, the bike came to a stop; therefore, negative acceleration, via braking this time, occurred again.
While all that was happening, some time went by.

Welcome! :)

Thank you so much!

 

[haruspex]

Relevant Equations:: I think v=u+at

That, as you note in the title, is a SUVAT equation. SUVAT equations only apply under a certain condition; what is it?
If a motorcyclist starts and finishes at rest, having been not at rest some time in between, can that condition apply?

So how come setting the initial and final accelerations as zero worked?
Setting a=0 and applying v=u+at gave you v=0, and it was from that that you found the answer. Instead, you could have simply set v=0 immediately, which would have been justified since you were told she started and finished at rest. So it was a case of two wrongs happening to combine to a right.