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A ball is dropped from the top of a towe...

A ball is dropped from the top of a tower 40 m high. What is its velocity when it has covered 20m? What would be its velcity when it hits the ground?

Text Solution

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Case I u=0
`a=-10m//s^(2)`
`S=-20m`
v=?
Using `v^(2)-u^(2)=2` as we get
`v^(2)-(0)^(2)=2(-10)(-20)`
or `v^(2)=400`
or `v=sqrt(400)=20m//s`
Case II: u=0
`a=-10m//s^(2)`
S=-40m
v=?
Using `v^(2)-u^(2)=2` as we get
`v^(2)-(0)^(2)=2(-10)(-40)`
or `v^(2)=800`
or `v=sqrt(800)=20m//s`
`=sqrt(400xx2)m//s`
`=20sqrt(2)` m/s
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