This is a problem from Cutnell and Johnson Physics(adsbygoogle = window.adsbygoogle || []).push({});

I have set up my formula so that eventually I am solving a quadtratic equation, I am unsure if my calculations are correct, any input would be appreciated.

THE QUESTION:

An airplane is flying with a velocity of 240 m/s at an angle of 30.0° with the horizontal. When the altitude of the plane is 2.4 km, a flare is released from the plane. The flare hits the target on the ground. What is the angle ?

WHAT WE KNOW:

Vo: 240 m/s

y = 2.4 km

Theta: 30 degrees

Beta : The unknown angle

MY CALCULATIONS:

Vo Sin 30 = Voy = -120 m/s (because it is in a downward direction, I think)

y = Voy(t) + 1/2ay(t^2)

-2,400 = -120(t) + 1/2(-9.80)(t^2)

In quadratic Form:

-4.9t^2 - 120(t) + 2,400 = 0

t = -120 +/- Sqrt (120^2 - 4(-4.9 x 2400))/2 x -4.9

THIS IS WHERE I GET CONFUSED

I am unsure if my signs are correct or if I am solving the formula correctly. I will go ahead and show the rest of my calculations but they are incorrect. (or could have been from the beginning)

t = 13.04 s

Vo cos 30 = Vox = 207 m/s

x = Vox(t) = 2699 m

Beta = tan^-1 y/x = tan^-1 2,400/2,699 = 41.64 degrees. <-----

*this answer is wrong, I am unsure where I made my error(s). Any help is greatly appreciated.

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# Homework Help: Flight and velocity.

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