# Math Help - Mechanics 1

1. ## Mechanics 1

a horizontal tunnel has a height of 3m. A ball is thrown inside the tunnel with an initial pseed of 18ms^-1. what is the greatest horizontal distance that the ball can travel before it bounces for the first time?

u_x=18
u_y=0

s_x=18t
s_y=-4.9t^2

thats is where i am stuck on.... I don't know what to do after this.
thanks

2. Originally Posted by MK47
a horizontal tunnel has a height of 3m. A ball is thrown inside the tunnel with an initial pseed of 18ms^-1. what is the greatest horizontal distance that the ball can travel before it bounces for the first time?

u_x=18
u_y=0

s_x=18t
s_y=-4.9t^2

thats is where i am stuck on.... I don't know what to do after this.
thanks
$s_y = -3 = -4.9t^2$

solve for t and sub the result into ...

$s_x = 18t$

3. I tried that many times,it gave me 14.08m but the answer from the book is 25.5m. Am I missing something here?

4. ever occur to you that "book answers" are occasionally in error?

use their "answer" and work backwards ... how high would the tunnel have to be?

5. ahhh yes,thank you.