Question

A particle moving in a straight line covers half the distance with speed of $3 ms^{-1}$. The other half of the distance is covered in two equal time intervals with speed of $4.5\, ms^{-1}$ and $7.5\, ms^{-1}$ respectively. The average speed of the particle during this motion is

• A. 5
• B. 5.5
• C. 5.8
• D. 4

Answer 1

Answer: (D)

4

Answer 2

Average speed of the particle for other half of the distances.
$A_{v} =\frac{2 \times 4.5 \times 7.5}{4.5+7.5}$
$=\frac{67.5}{12}=5.62$
Again, the average speed of the particle
$A_{v} =\frac{2 \times 5.63 \times 3}{5.63+3}$
$=3.9 \,m / s =4 \,m / s$