Question

A stair case contains three steps having height 10

cm each. If each are 20 cm wide then the

minimum horizontal velocity of a ball moving off

the upper mark plane so as to hit the lowest plane

directly is

(a) 4 m/s (b) 2 m/s (c) 1 m/s (d) 0.5 m/s​

Answer 1

Answer:

(b)2m/s

Step-by-step explanation:

Answer 2

ANSWER

h= height

w= width of each step

O= uppermost plane  

A= lowermost plane

Consider the ball roll from the upmost plane O with horizontal velocity v here the vertical velocity in the y direction will be 0

X=vt

t = x/v........(1)

The horizontal range of the ball lies between 2wand3w  

Horizontal range x of the ball will be greater than 2w.

h = 10cm = 0.10m

w = 20cm = 0.20m

x> 2w

x > 0.40

The ball travels form plane O to plan A=2h

equation of motion =

s = ut + 1/2 at^2

u = 0

2h = ut + 1/2 gt^2

t = u8ndre root 4h/g

from 1 and 2

v = > 2m/s