Help---- projectile problem---Thanks (1 Viewer)

[Tianshu]

QUIZ One

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

Quiz Two

A gun is aimed at a target on the ground 150m away. If the initial velocity is 125m/s, find the angles at which the gun could be fired to reach the target? (use g =10)


Really appreciate for your help!!!:wave:

 

[z600]

For the first one i got 4 degrees

Why are you doing projectile motions in year 10?

 

[watatank]

first answer:

consider the y direction

s = ut + 0.5 at²

u = 0 (from rest), then accelerates

s = 0.5at²

a = 10, s = 6


6 = 0.5*10*t²
= 5t²

t = rt(6/5)

consider x direction

s = ut + 0.5 at²

or simply s = ut (since there is no acceleration in x direction)

u = s/t

= 2 / [ rt(6/5) ]

i lack calculator you can do the rest

 

[Tianshu]

Thanks a lot!!!
Anyone get any math method?
for the first Question, the answer is 18 degrees!