A ball rolls off the edge of a horizontal table top 4 m high. If it strikes the floor at a point 5 m horizontally away from the edge of the table, what was its speed at the instant it left the table?

Options

A. `2.5 ms^(-1)`
B. `3.5 ms^(-1)`
C. `5.5 ms^(-1)`
D. `6.5 ms^(-1)`

Answer

C

Explanation

Using, `h = (1)/(2) g t^(2)`, we have

`h_(AB) = (1)/(2)g t_(AC)^(2)`
or `t_(AC) = sqrt((2h_(AB))/(g)) = sqrt((2 xx 4)/(9.8)) = 0.9s`
Further, `BC = vt_(AC)`
or `v = (BC)/(t_(AC)) = (5)/(0.9) = 5.55 ms^(-1)`