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## Homework Statement

hi guys ,, got this problem about projectile ,,

A ball is thrown from the top of a building with a velocity of 40 m/s at an angle of 53

with the horizontal. After 2 s, it is seen to be at height of 84 m above the ground.

a) Find the height of the building

b) At which other time will the ball again be at a height of 84 m?

c) If the ball hits a wall at a height of 52 m above the ground, what is the distance of the

wall from the building?

d) Find the magnitude and direction of the velocity of the ball when it reaches the wall

## Homework Equations

## The Attempt at a Solution

i tried to get the height of the building by 84+h(b)=40sin(53)*2-9.8*4 ,, and I got h(b)=59.31m ,, anyway ,, the way is right ?? ,, and about (b) i tried to get the second time ,, but i get it negative (59.31+84=40sin(53)x-9.8*x^2 = 9.8x^2-40sin(53)x-143.31 and i get x=5.7 , x=-2.5 and i think it's wrong because none of them equal 2 ,, and one of them should equal 2 ,, any ideas what did I do wrong here ?