BITSAT 2015 Paper

For the blocks A and B FBD as shown below

Equations of motion
aA =

F

M

(in x direction)
aB =

F

M

(in x direction)
Relative acceleration, of A w.r.t. B,
aA,B = aA−aB = -

F

m

−

F

M

= - F (

M+m

Mm

) (along – x direction)
Initial relative velocity of A w.r.t. B,
uAB = v0
using equation v2 = u2 + 2as
0 = v02 -

2F(m+M)

Mm

⇒ S =

Mmv02

2F(m+M)

i.e., Distance moved by A relative to B
SAB =

Mmv02

2F(M+m)