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# M2 edexcel help!!! (projectiles) watch

1. ok the question is Q31 from review exercise 1
(i) a particle P is projected with a velocity (14i +21j)ms-1 from O on the horizontal ground and moves freely under gravity. At T seconds after projection, P strikes the ground at the point C. Find...
a) T
b) distance OC
c)the position vector H, the point at which P achieves its greatest height above the ground.

I don't know where to start
2. Remember that horizontal and vertical motion can considered separately.

What's the criterion for P striking the ground?
3. (Original post by neetz0790)
ok the question is Q31 from review exercise 1
(i) a particle P is projected with a velocity (14i +21j)ms-1 from O on the horizontal ground and moves freely under gravity. At T seconds after projection, P strikes the ground at the point C. Find...
a) T
b) distance OC
c)the position vector H, the point at which P achieves its greatest height above the ground.

I don't know where to start
this question is actually straight forward ... so what u have to do is to seperate the horizontal motion and the vertical motion... as you got the speed in the I's and J's notation u know exactly what the initial vertical velocity... in this case it is 21 m/s
so for part (i) you know that the displacement is 0 ... this is because the particle comes back to the point where it took off...
s=ut+1/2at^2
0=21t+4.9t^2

t=0 or t=30/7

i hope u agree with that...
4. thx guys that helped (and it was 30/7 ) thx again

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