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December 21, 2014

December 21, 2014

Posted by **Anonymous** on Friday, January 2, 2009 at 10:44pm.

I'm thinking I should be setting two kinematics equations equal to each other, but I don't know which ones.

- Physics -
**drwls**, Friday, January 2, 2009 at 11:15pmFor the balloon,

Y = 7 t + 12

where t is the time the pellet is fired.

For the pellet,

Y = 30 t - (g/2) t^2

= 30 t - 4.9 t^2

Solve for the two t's when the Y's are equal.

4.9 t^2 - 23 t +12 = 0

Note that this is a quadratic equation with two roots.

Then use either Y equation to get the corresponding altitudes at those two times.

- Physics -
**Anonymous**, Friday, January 2, 2009 at 11:39pmHow did you get the pellet equasion? And how did you simplify it without knowing the value of g?

- Physics -
**Damon**, Saturday, January 3, 2009 at 5:16amHe used g = 9.8

(1/2) g = 4.9

For constant acceleration

x = Xo + Vo t + (1/2) a t^2

here

height = initial height + 30 t - 4.9 t^2

- Physics -
**Anonymous**, Saturday, January 3, 2009 at 2:17pmO right, gravity is 9.8

thanks!

- Physics -
**Kayline**, Wednesday, October 13, 2010 at 9:42amSo, because of the constant speed of the ballon, we considere (1/2)*g*tē for the balloon to be 0 ?

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