$A$ person walks along a straight road from his house to a market $2.5 \,km$ away with a speed of $5 \,km/h$ and instantly turns back and reaches his house with a speed of $7.5 \,km/h$. The average speed of the person during the time interval $0$ to $50 \,min$ is (in $m/s$)

Write the relation between speed and the magnitude of velocity.

$A$ body travelling along a straight line path travels the first half of the distance with a velocity of $7 \,m/s$. During the travel time of the second half of the distance, the first half of the time is travelled with a velocity of $14 \,m/s$ and the second half of the time is travelled with a velocity of $21 \,m/s$. Then the average velocity of the body during the entire journey is: (in $\,m/s$)

$A$ car covers $2/5^{th}$ of the total distance with speed $v_1$ and $3/5^{th}$ of the total distance with speed $v_2$. What is its average speed?

Why can the speed of a moving object never be negative?

$A$ body moves in a straight line with speeds $v_1$ and $v_2$ for distances which are in the ratio $1: 2$. Find the average speed.