A staircase contains three steps each 10 cm high and 20 cm wide. What should be the minimum horizontal velocity of the ball rolling off the uppermost plane so as to hit directly the lowest plane? (in ms-1)

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,θ=0∘y=tan⁡θ−gx2sec2⁡θ2u2where g = 10 ms-2 = 1000 cm s-2−20=−8000002u2u=200cms−1=2ms−1II method:R=u2hg 0.4=u20.210 u=2m/s