Physics problem

Discus: SAT/ACT Tests and Test Preparation: October 2003 Archive: Physics problem
 By Bard (Bard) on Sunday, October 12, 2003 - 08:22 pm: Edit

A ball is thrown horizontally from the roof of a building 9m tall and lands 8.5m from the base. What was the balls initial speed.( i got 4.6 but i think im wrong.

 By Montydsw11 (Montydsw11) on Sunday, October 12, 2003 - 08:29 pm: Edit

The answer is 6.29 m/s in the X direction, please let me know if you need me to explain...

 By Bard (Bard) on Sunday, October 12, 2003 - 08:36 pm: Edit

hi monty can u explain this one for me? I know I am supposed to look for inital velocity in the x direction but i am unable to get 6.29

Thank You

 By Montydsw11 (Montydsw11) on Sunday, October 12, 2003 - 08:43 pm: Edit

The equation u need=
delta x=(vknot x time) + .5(at)^2

First, solve for time in the Y direction, you know acceleration in the Y is -9.8 (acceleration in the X is always 0, by the way).

Secondly, once you get time in the Y, you can use that for time in the X. I think I got 1.39 for time. Next, just use the same equation and solve for v knot.

 By Montydsw11 (Montydsw11) on Sunday, October 12, 2003 - 08:44 pm: Edit

dont forget to use negative 9 for your displacement in Y...

Let me know if you get it this time...

 By Bard (Bard) on Sunday, October 12, 2003 - 09:04 pm: Edit

hey man thnx a lor I understand the problem now and how to get it.

 By Hsimpson2k4 (Hsimpson2k4) on Sunday, October 12, 2003 - 09:14 pm: Edit

lol it is v naut not know (naut as in 0)