Hey(adsbygoogle = window.adsbygoogle || []).push({});

Just need a little help with *another* accelerated linear motion question, any help is appreciated:

(A) A particle starts from rest at a point p and accelerates at 2m/s^2 until it reaches a speed v m/s.

It travels at this speed for one minute before delerating at 1m/s^2 to rest at q. The total time for the journey is 2 minutes.

(i) calculate the distance pq

(ii)If a second particle starts from p at time t=0 and moves along pq with speed (2t + 50) m/s, find the time taken to reach q.

Part one ive gotten out - pq = 3600m

Part two, im not really too sure where to start.

(B) A particle P is projected vertically upwards with an initial velocity u and two seconds later a second particle Q is projected vertically upwards from the same point with initial velocity 1.5u. Calculate, in terms of u, how long W is in motion before it collides with p, and prove that u > 9.8.

Ok, so ive made a bit of a start on this one, whether or not its right is what im trying to find out, and what i go about doing next:

Eqn1 : S=ut+(1/2)at^2

Eqn2 : S=ut-(1/2)gt^2

S=ut-(1/2)gt^2

s=(1.5u)(t+2) - (1/2)g(t+2)^2

s=1.5ut+3u-(1/2)g(t^2+4t+4)

s=1.5ut+3u-(1/2)gt^2-2g-2gt

Collision occurs when s=s

ut-(1/2)gt^2 = 1.5ut+3u-(1/2)gt^2-2g-2gt

ut=1.5ut+3u-2gt-2g

2ut+3ut+6u-4gt-4g

-ut+4gt=6u-4g

t(4g-u)=6u-4g

t= (6u-4g)/(4g-u)

So thats all that ive got so far, any help very appreciated

Thanks again

**Physics Forums | Science Articles, Homework Help, Discussion**

Dismiss Notice

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Acc Linear Motion

**Physics Forums | Science Articles, Homework Help, Discussion**