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**1. Homework Statement**

A rock is thrown horizontally from a tower point A, and hits the ground 3.5 s later at point B. A line from A to B makes an angle of 50 degrees with the horizontal.

Compute the magnitude of a initial velocity u of the rock.

**3. The Attempt at a Solution**

I started looking at the motion in x direction, which is

u the unknown.

Then i looked at the motion in y direction:

And here we have the gravity.

so i used the formula:

s=1/2 * g * t^2

1/2*9.81*(3.5)^2 =60 m/s^2

from trigonometry

tan(50)=60/x

solving x i get 50.34 meters

But I'm not sure if I have done it corretly.

Thank you for your help.