Question

A firefighter crew uses a water cannon that shoots water at 30.0 m/s at a fixed angle of 48.0 degrees above thr horizontal. The firefighters want to direct thr water at a blaze that is 10.0m above ground level.

How far from the buildibg should they position their cannon? There are two possibilities (d1<d2); can you get them both? (hint:start with a sketch showing thr trajectory of water.)

Please express d1 and d2 in meters and explain please, thank you!

Answer 1

So we have two possible distances as,

Both distances expressed in three significant figures.

while solving for time I have used the following kinematic relation,

In general the relation between displacement   of object in time under constant acceleration having initial velocity ( directed along the line parallel to direction of displacement ) given as,

Note that if the acceleration is directed in the opposite direction of initial velocity we will use the negative value of of a in above equation as was the case in our case .