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Atoms And Molecules

Question
CBSEENSC9006078

A ball thrown up vertically returns to the thrower after 6 s. Find:
(a) the velocity with which it was thrown up,
(b) the height, and
(c) its position after 4 s.

Solution

Time space of space ascent space equals space time space of space descent space equals space 6 over 2 space equals space 3 space sec space
straight i right parenthesis space For space upward space motion space of space the space ball comma
space
straight v space equals space 0 comma space straight t equals space 3 space straight s comma space straight g space equals space minus 9.8 space straight m divided by straight s squared

Using space the space formula comma space

space space space space space space space space straight v space equals space straight u plus gt

0 space equals space straight u space minus space 9.8 cross times 3

straight u space equals space 9.8 space cross times space 3

space space space equals 29.4 space straight m divided by straight s comma space is space the space initial space velocity.

ii right parenthesis thin space Height space is space given space by comma space

straight s space equals space ut space plus space 1 half gt squared space
space space space equals space 29.4 space cross times space 4 space minus 1 half cross times 9.8 cross times 4 squared
space space space equals space 88.2 space minus space 44.1

space space space equals space 44.1 space straight m

iii right parenthesis thin space The space position space of space the space ball space after space 4 space sec space is space given space by comma space
straight s space equals space ut space plus space 1 half gt squared space
space space space equals space 29.4 space cross times 4 space minus 1 half cross times 9.8 cross times 4 squared space
space space space equals space 117.6 space minus space 78.4

space space space equals space 39.2 space straight m

That space is comma space the space ball space is space at space straight a space height space 39.2 space straight m space from space the space ground.