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A ball is dropped from the top of an 80 m high tower After 2 s another ball is thrown downwards from the tower. Both the balls reach the ground simultaneously. The initial speed of the second ball isA. `10 m//s`B. `20 m//s`C. `30 m//s`D. `40 m//s` |
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Answer» Correct Answer - C Let the first ball reaches the ground after time t, the second ball will take time `(t-2)`. `80=1/2g t^(2)impliest=4 s` Let u: initial velocity of the second ball `80=u(t-2)+1/2g (t-2)^(2)` `=u(4-2)=1/2xx10(4-2)^(2)` `=2u+20` `u=30 m//s` |
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