# physics

a projectile is ejected from a 25 m high tower with a velocity of 40 m/s at an angle of 30 degrees to the horizontal first on Earth and then on Mars. What is the ratio of the time taken to hit the ground on Mars compared to Earth? (Assume gravity on mars = .38gEarth)

I keep getting 1.6 seconds. Please help me, with steps to solve if possible. I know its a long problem. Thank you so much in advance!

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1. hf=hi+vi*t-1/2 g t^2

first, I am wondering is the 30 degrees above horizontal, or below horizonal. I will work it as ABOVE horizontal.

vi vertical= 40*sin30=20m/s

-25=0+20t-g/2 t^2
solve for t

t^2-40t/g -25-0

t= 20/g +- sqrt (400/g^2 + 25)

tearth=you do it.
tMars = you do it, g=.38*9.8

check my math.

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2. That doesn't work out to the correct answer. I worked it the same as you but I get 1.4 instead of 2.4.

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posted by kjean

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