• # question_answer A strip of wood of length l is placed on a smooth horizontal surface. An insect starts from one end of the strip, walks with constant velocity and reaches the other end in time ${{t}_{1}}$. It then flies off vertically. The strip moves a further distance l in time ${{t}_{2}}.$ A) ${{t}_{1}}={{t}_{2}}$ B) ${{t}_{1}}>{{t}_{2}}$ C) ${{t}_{1}}<{{t}_{2}}$ D) none

 If $v$ is the velocity of insect and $v$ is the velocity of strip (opposite direction), then $l=\left( v+u \right){{t}_{1\,}}$ $\therefore {{t}_{1}}=\frac{\ell }{\left( v+u \right)}$ When insect fly off, ${{t}_{2}}=\frac{\ell }{u}$ Clearly, ${{t}_{2}}>{{t}_{1}}$