Question

*STRAIGHT OBJECTIVE TYPE*
A ball is dropped from the top of a building the ball takes 0.5 seconds to fall past the three metre length of a window some distance from the top of the building if the velocities of the ball at the top and at the bottom of the window areVB and VB respectively, then(take g=10m/s^2)
A. VT+VB =12m/s
B. VT-VB =12m/s
C. VB.VT =1m/s
D. VB/VT =1m/s

Answer 1

Let initial velocity at top of window be 'u' and velocity at bottom be ' v'  

Use S = ut + 1/2at2   where u is initial velocity a =g(10) t =0.5  S =3 ,. We get value of u as 3.5m/S. Now use v = u + at  where u is initial velocity and a =g,t =0.5 you will get the value of v now use it to find u-v ,v+v ,u.v