The least velocity
Classical Mechanics
Level
2
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(in m/s)
4
2
0.5
1
This section requires Javascript.
You are seeing this because something didn't load right. We suggest you, (a) try
refreshing the page, (b) enabling javascript if it is disabled on your browser and,
finally, (c)
loading the
non-javascript version of this page
. We're sorry about the hassle.
1 solution
To hit directly the lowest plane the ball has to cross the point B. From A to B, the ball has to travel to horizontal distance equal 40cm =40m and vertical distance of 20cm=0.2m.
Let the time taken to reach point be t.u=0 m/s h=0.2m from the equation, h=ut+1/2gt²
we get 0.2=0+1/2 x9.8 t² t²=0.4/9.8 t²=0.04 t=0.2 Let v be the horizontal velocity of ball than the horizontal distance travelled by the ball=0.2v in order to clear the point B it must be equal to 0.40. 2v=0.4 v=2m/s ∴So minimum velocity required to to hit the lowest floor is 2 m/s