A staircase contains three steps each 10 cm high and 20 cm wide figure. What should be the minimum horizontal velocity of a bal rolling off the upper most plane so as to hit directly the lowest plane?

Answer

`(2)`

Explanation

At minimum velocity, it will move just touching point `E` reaching the ground. A is the origin of reference coordinate.
If `u` is the minimum speed,
`x = 40, y = 20, theta = 0^@`
`y = tan theta - g (x^2 sec^2 theta)/(2 u^2)`
where `g = 10 ms^-2`
=`1000 cm s^-2`
`-20 = (800000)/(2 u^2)`
`u = 200 cm s-1 = 2 m s^-1`.
.