Particle question

A particle moves s metres in a time t seconds so that s = 2t^2-6t+5. What is the distance travelled before it comes to rest?

(a) 3 metres
(b) 3.5 metres
(c) 4 metres
(d) 1.5metres

Not having much fun with this question, the value I get isn't even in the list.

Reply 1

JullittaO73

Original post

by Peter Bullock

A particle moves s metres in a time t seconds so that s = 2t^2-6t+5. What is the distance travelled before it comes to rest?
(a) 3 metres
(b) 3.5 metres
(c) 4 metres
(d) 1.5metres
Not having much fun with this question, the value I get isn't even in the list.

Talk us through your working, then, and let's see where there could be a problem 🙂 and you're sure that's the full question?

(edited 3 months ago)

Reply 2

Skybird

Given s = 2t^2 - 6t +5

The derived function I get is :

dy/ dx = 4t - 6

When the particle comes to rest the velocity is zero

Hence

4t - 6 = 0

So, t = 3/2s or 1.5s

Substituting t = 1.5 into the equation for s gives me s = 0.5 metres

I think 0.5 is the answer.

I don't have much confidence in this subject and want to build more, I do know however that at times textbook answers can be wrong.

What am I missing here?