A strip of wood of mass `M` and length `l` is placed on a smooth horizontal surface. An insect of mass `m` starts at one end of the strip and walks to the other end in time `t`, moving with a constant speed. The speed of the insect as seen from the ground is

Options

A. `l/t(M/(M+m))`
B. `l/t(m/(M+m))`
C. `l/t(M/m)`
D. `l/t(m/M)`

Answer

A

Explanation

`m(l-x)=Mximpliesx=(ml)/(m+M)`
distance moved by insect w.r.t ground in
`l-x=l-(ml)/(m+M)=(Ml)/(m+M)`
`"Speed" =("distance")/("time")=(Ml)/(t(M+m))`