A $100\, m$ long train is moving with a uniform velocity of $45\, km/hr$. The time taken by the train to cross a bridge of length $1 \,km$ is.........$s$

A particle covers half of its total distance with speed $v_1$ and the rest half distance with speed $v_2 .$ Its average speed during the complete journey is 

A body covers first one-third of the distance with a velocity $20\, ms^{-1}$, the second one-third with a velocity of $30\, ms^{-1}$ and last one-third with a velocity of $40\, ms^{-1}$. The average velocity is nearly........$m/s$

A man walks on a straight road from his home to a market $2.5\; km$ away with a speed of $5 \;km h ^{-1} .$ Finding the market closed, he instantly turns and walks back home with a speed of $7.5 \;km h ^{-1} .$ What is the average speed (in $km/h$) of the man over the interval of time $0$ to $50\; min$ ?

A train has a speed of $60\, km/h$. for the first one hour and $40\, km/h $ for the next half hour. Its average speed in $km/h$ is

Define speed. Define average speed.