Velocity vs Speed (What's more relevant here?)

[Slimy0233]

Homework Statement

5. A particle starts from rest with a constant acceleration.
At a time t second, the speed is found to be 100 m/s and
one second later the speed becomes 150 m/s. Find (a) the

acceleration and (b) the distance travelled during the
(t+1)th second.

Relevant Equations

$v = {a}{t}$

This is a famous book in India. I was wondering if one could say if the answer should include velocity or speed. I mean, I don't think there are any details which hint at velocity. We are gives speed in the question and we are asked to find out the distance traveled, this hints we are asked to calculate speed, not velocity. Is it right for the author to calculate velocity (I don't think the calculations makes sense for velocity)?

 

[hmmm27]

I was wondering if one could say if the answer should include velocity or speed.

"speed" is fine within the context of the problem. One assumes the "constant acceleration" is linear, so its speed is just the magnitude of the velocity.

I mean, I don't think there are any details which hint at velocity.

You mean like the first sentence in the problem statement ?

 

[Slimy0233]

"speed" is fine within the context of the problem. One assumes the "constant acceleration" is linear, so its speed is just the magnitude of the velocity.

You mean like the first sentence in the problem statement ?

Constant acceleration is the reason why the author wrote velocity instead of speed. I mean, in this case (due to constant acceleration) both are equal. PS: This is motion in 1d, but even with 1d there's a problem of which direction it's moving in. Since it's constant acceleration, it has to move in only one direction.

> You mean like the first sentence in the problem statement ?

No, I meant they had asked us to calculate the distance travelled. So, I thought, they are asking us the speed (they are, but speed = vel here as you know, so we don't really care what we call it)

edit: Thank you for your help! I consider this solved :)

 

[kuruman]

In this case speed and velocity can be used interchangeably. That's because the particle starts from rest which means that at all times the velocity and the acceleration are in the same direction. The possibility that the particle reverses direction between $t$ and $t+1~$(s) is excluded.

 

[hmmm27]

So, I thought, they are asking us the speed (they are, but speed = vel here as you know, so we don't really care what we call it)

Well, since the problem doesn't explicitly state the direction, we don't know how it lines up with a theoretical pre-established reference frame.

Fair enough, technically

But, without further information/sneakiness, "in the direction it started off at" seems a reasonable assumption to use as a positive reference.