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How long until the ball hits the ground? 
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#1
Aug2511, 12:56 AM

P: 25

1. The problem statement, all variables and given/known data
A ball is thrown downward from a height of 30m at 8m/s. How long until it hits the ground? (Air resistance is negligible and gravity is 9.8m/s 2. Relevant equations I tried deltaX=Vi+(1/2)a(t^2) and came out with 2.12, but the solution says it's 1.79. 3. The attempt at a solution 30=8+(1/2)(9.8)(t^2) 22=4.9(t^2) sqrt4.49=sqrt(t^2) t=2.12 


#2
Aug2511, 01:47 AM

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P: 4,300

Are you not missing a t?
[tex]V = V_i + a t[/tex] so [tex]\Delta x = V_i \mathbb{t} + \frac12 a t^2[/tex] 


#3
Aug2511, 02:16 AM

P: 25

Thank you, but I'm afraid I'm evenb more confused by the additional t.
I ended up at 308t=4.9(t^2) What I keep doing after that seems to make it more complicated than it should be. COuld you possibly point me in the right direction? Thank you for your time. 


#4
Aug2511, 03:27 AM

Sci Advisor
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P: 4,300

How long until the ball hits the ground?
It's a standard quadratic equation, of the form ax^{2} + bx + c = 0.
How do you solve one of those? 


#5
Aug2511, 05:55 PM

P: 25

Ah... hate when I over look simple things. Thank you very much.



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