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A ball is thrown in the air @ 30m/s... 
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#1
Jul509, 11:17 PM

P: 11

1. The problem statement, all variables and given/known data
A ball is thrown straight up with an initial speed of 30m/s, (a) Show that the time it takes to reach the top of its trajectory will be 3 seconds. (b) Show that it will reach a height of 45m (neglecting air resistance). 2. Relevant equations Earth's gravity = 9.8 meter/secondē (Professor said to just round it to 10). Equation unknown. d=1/2(g)tē ? 3. The attempt at a solution (a) Played around with Subtracting negative 9.8m/sē (is it considered negative since the ball gets thrown up?  Instead of it coming down?). (b) 45m = 1/2(9.8m/sē)tē  I figure I need to know "t" before I could solve this. 


#2
Jul509, 11:28 PM

HW Helper
P: 5,341

If something starts out at 30 m/s and slows 10 m/s every second, it will reach 0 m/s in how many seconds? Here are some formulas for you: http://www.physicsforums.com/showpos...63&postcount=2 These lessons might be helpful: http://www.glenbrook.k12.il.us/gbssc...ors/u3l2c.html 


#3
Jul509, 11:39 PM

P: 11

Thanks a bunch. Will get started on the lesson.. then try the problem again.



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