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April 24, 2014

April 24, 2014

Posted by **bob** on Thursday, August 9, 2012 at 7:24pm.

- physics -
**MathMate**, Thursday, August 9, 2012 at 9:06pmAssume no air resistance.

For the object thrown downwards,

t=4 s

vi=-10 (+ve upwards)

g=-9.8 m/s²

S=vi*t+(1/2)gt²

=-10*4+(1/2)(-9.8)(4²)

=-118.4 m

For the object thrown downwards,

t=unknown

vi=+10 (+ve upwards)

g=-9.8 m/s²

S=vi*t+(1/2)gt²

-118.4=+10*t+(1/2)(-9.8)(t²) ...(1)

Solving the quadratic equation (1), we get

t=-4 or t=296/49

Can you take it from here?

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