Math Is Fun Forum

Au101

Member

Registered: 2010-12-01

Posts: 353

Instantaneous Rest - Kinematics

Hi,

I was wondering if anybody could help me out by reminding me how to find the times at which a particle comes instantaneously to rest - I can't seem to remember how to do it. I think one has to let the velocity = 0, or perhaps the acceleration, but neither of these seem to get me the right answer, as I can only get one value of t and the question implies that there should be more.

In case it is helpful, and so as to make it clear what I am talking about, here is the question:

A particle moves along a straight horizontal track such that its displacement s metres, from a fixed point O on the line after t seconds is given by

(a) Find the values of t for which the particle is at O.

Unless I'm very much mistaken the solutions to part a are

(b) Find the values of t at which the particle comes instantaneously to rest.

Thanks!

Last edited by Au101 (2010-12-15 02:11:11)

soroban

Member

Registered: 2007-03-09

Posts: 452

Re: Instantaneous Rest - Kinematics

. Right!

.

Au101

Member

Registered: 2010-12-01

Posts: 353

Re: Instantaneous Rest - Kinematics

Ahhh, I see, thanks very much Soroban, I had made a mistake in the differentiation and hence could only get one positive value of t. Thanks again!:)