Trial Q (1 Viewer)

[krypticlemonjuice]

In this Q, why do the answers calculate the angle of initial velocity to the vertical instead of the horizontal???

 

[krypticlemonjuice]

Part a for reference

 

[howcanibesmarter]

because you are trying to find the spray angle, not the angle of elevation/depression like a typical projectile question.

Just draw your right angle triangle. You have uy going downwards at 1.43ms^-1, and to the left is 3.08ms^-1. Using tan^-1 u get 65 degrees, but that is only half of the spray angle. Thus u times by 2 to get 130 degrees.

If you did to the horizontal instead you wouldve gotten 90-65 so 25 degrees below the horiztonal which is not what the question was looking for.

 

[krypticlemonjuice]

because you are trying to find the spray angle, not the angle of elevation/depression like a typical projectile question.

Just draw your right angle triangle. You have uy going downwards at 1.43ms^-1, and to the left is 3.08ms^-1. Using tan^-1 u get 65 degrees, but that is only half of the spray angle. Thus u times by 2 to get 130 degrees.

If you did to the horizontal instead you wouldve gotten 90-65 so 25 degrees below the horiztonal which is not what the question was looking for.

Hmm, you reckon you could draw me a diagram if you don't mind making it clear the angle we are calculating?

 

[howcanibesmarter]

lmk if its unclear still