Projectile Motion from 3U Fitzy (1 Viewer)

[The Kaiser]

Could you superiorly talented people, help me with some questions (which I have absolutely no idea how to attempt) on Projectiles on Fitzpatrick 3 Unit. Thanks in Advance.

Exercise 25(d)

13. A particle is projected with a speed of 25 m/s in the direction of a point P distant 24m away horizontally and 7m Vertically above the point of projection.

a) Find the coordinates of the point of the trajectory below P
b) At the instant of projection of the particle, a second particle is dropped from P. Prove that the two particles will collide.

24. Find the speed and direction of a particle which, when projected from a point 15m above the horizontal ground, just clears the top of a wall 26.25m high and 30m away.

Thanks Again

 

[Timothy.Siu]

a)y''=-g y'=-gt+k=25sin A when t=0 k=25sin A y'=-gt+25sin A
y=-0.5gt^2+25sin A.t

x''=0 x'=k=25cos A x=25cos A.t
A=tan^-1 7/24
sin A=0.28 cos A=0.96

find time when x=24
25x0.96 t=24 t=1
therefore when the projectile reaches 24m horizontally t=1
sub into y
y=-5+25x0.28
=2

therefore (25,2) is the coordinate under P that the projectile reaches

b)
the other thing y''=0 y'=-gt+K y'=0 k=0 y'=-gt
y=-0.5gt^2+K
t=0 y=7 (initial point where P is)
k=7
y=-0.5gt^2+7
when t=1 y=2 therefore they collide

sorry about my K's they should be different constants..
i'lll try do the next one now...and yeah probably too much useless working out but i'm still learning

 

[The Kaiser]

Thanks, I understand how to the first question now. (I Forgot that I could find t, because I was dependant on the cartesian equation in terms of x).

But for the second question I don't know where to start.

 

[Timothy.Siu]

ok i got it, it means the vertex is that point,

 

[The Kaiser]

ok i got it, it means the vertex is that point,

Oh, if that's the case then that's easy...

Could you just put your working out just to double check

First you find Vsin(a) then use it to find the time to reach the maximum height and then find Vcos(a) then find tan (a) etc, is that right.