Question

A bird flies in straight line for $4s$ with a velocity $v=(2t-4)m/s$. What is the distance covered by the bird in returning to the place from where it started its journey? (in metres)

• A. $6$
  
• B. $7$
  
• C. $8$
  
• D. $9$
  

Answer 1

The correct option is C $8$

the block will move in straight line in negative direction initially as v=-4 at t=0, and will move in +ve x direction after 2 sec as v=0 at t =2 sec.

Displacement by the bird in first 2 sec will be $\int vdt=S$

$\int (2t-4)dt=S$ limits of time is 0 sec to 2 sec.

$S=t^2-4t$ limits of t is 0 and 2.

$S=-4$ also if limits are 0 to 4, $S=0$ means he will come back to its initial position after 4 sec.

total distance will be 2 times the displacement at t=2 sec means 8 meters.

so best possible option is option C.