Hey I was wondering if anyone can help me on this problem below :)

The velocity of a particle moving in a straight ine with uniform acceleration increases from 10m/s to 20m/s in 30m. When and where was the velocity 15m/s


Thx:D

v^2 = u^2 + 2as
(v = init vel, u = fin vel, a - accel, s = displacement)

solving for a gives: a = (v^2 - u^2)/2s

since the particle accelerated from 10m/s to 20m/s in 30m...

a = (20^2 - 10^2)/2*30
a = 5 m/s^2

back to v^2 = u^2 + 2as

solving for s:
s = (v^2 - u^2)/2a

this time the final velocity is 15 and we want s

s = (15^2 - 10^2)/2*5
= 11.5m

and as v = u + at

t= (v - u)/a
= (15-10)/5 = 1s

sothe velocity was 15m/s after 1s and 11.5m

hope I'm right and hope it makes sense... it's been a while since I've had to do these and it was fun dredging those equations of motion back from my memory.

a

Hi agneau, this looks right to me

However I recommend when the question is clearly homework, it's often more suitable to hint, rather than to give the full answer, this helps the OP to learn, rather than just copy down the answer.

If the OP has obviously tried to have a go at the problem, then we generally help a little more. The effort we give them depends on the amount of effort they give us.

Welcome to the site :)