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## Homework Statement

You are on the roof of a building that is 150 m tall armed with a tennis ball launcher that fires tennis balls with a speed of 35 m/s. Another building is 100 m away from your building. You are trying to fire a tennis ball into a window of the other building that is 10 m below your current height. Knowing that the ball will fall as it travels, you first align the launcher so that it is completely horizontal, hoping that it will fall the necessary 10 m as it reaches the building.

(a) How long does it take for the ball to reach the building?

(b) Does the ball go through the window? If not, where does the ball hit the building?

(c) If you want the ball to go through the window, at what angles could you aim the launcher? (NOTE: There are two angles that work! Find both!)

(d) For each angle in (c), find the time for the ball to reach the window.

(e) Sketch the two trajectories that the ball could take to go through the window. Explain why the times you found in (d) are different.

ANSWERS: (a) 2.86 s (b) no, 30 m below window (c) One angle is 19.2°. The other is greater than this.

(d) The time for 19.2º is 3.03 s. The other time is longer than this. (e) Show me. Tell me.

## Homework Equations

x=xo + vxo*t

y= yo + vyo* t - (1/2)gt

## The Attempt at a Solution

i know what to do for A and B, but i am on C and i don't know how to find the angle. My teacher gives the answers so i know one of the angles but i don't know how he got it.