Projectile Motion Qs :( (1 Viewer)

[~Theta~]

Hello everyone. If anyone could post solutions for the following two questions, that would be fantastic.

1. A horizontal drainpipe 6m above sea level empties stormwater into the sea. If the water comes out horizontally and reaches the sea 2m out from the pipe, find the initial velocity of the water, correct to 1 decimal place. Let g be 10ms^(-2) and neglect air resistance.

Aaaand...

2. A gun is aimed at a target on the ground 150m away. If the initial velocity is 125ms^(-1), find the angles at which the gun could be fired to reach the target.

That's it, thanks for your time.

 

[Timothy.Siu]

umm for the first one, u write out the equations for x and y

x=Vt
y=-0.5gt^2+6
t=x/V
sub t into y equation

y=-0.5x10.x^2/V^2+6
sub in point (2,0)
0=-20/V^2+6
V^2=20/6
V=sqrt(10/3)
i hope thats right.

second Q.
x=125cos A.t
y=125sin A.t-0.5gt^2
t=x/125cos A
sub it in,

y=xtan A-5x^2/(125^2.cos^2 A)
sub in point (150,0)
0=150tan A-(1+tan^2 A)x5x150^2/125^2
expanding and moving to one side,

7.2tan^2 A-150 tan A+7.2=0
then quadratic equation
i got A=87 degrees 15 minutes (nearest minute)
or degrees 45 minutes (nearest minute)

 

[~Theta~]

umm for the first one, u write out the equations for x and y

x=Vt
y=-0.5gt^2+6
t=x/V
sub t into y equation

y=-0.5x10.x^2/V^2+6
sub in point (2,0)
0=-20/V^2+6
V^2=20/6
V=sqrt(10/3)
i hope thats right.

Oh thank you!

Just to clarify, is there no sin @ or cos @ because the angle is 0?

 

[Timothy.Siu]

Oh thank you!

Just to clarify, is there no sin @ or cos @ because the angle is 0?

well u can pretend there is, but then u get sin 0=0 and cos 0=1
thats basically wat i did, just didn't write it