A car travels a distance of $x$ with speed $v_1$ and then same distance $x$ with speed $v_2$ in the same direction. The average speed of the car is
$\frac{ v _1 v _2}{2\left( v _1+ v _2\right)}$
$\frac{v_1+v_2}{2}$
$\frac{2 x }{ v _1+ v _2}$
$\frac{2 v _1 v _2}{ v _1+ v _2}$
A cyclist starts from the centre $O$ of a circular park of radius one kilometre, reaches the edge $P$ of the partk. Then cycles along the circumference and returns to the centre along $QO$ as shown in the figure. If the round trip takes ten minutes, the net displacement and average speed of the cyclist (in metre and kilometre per hour respectively) is
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 body has speed $V, 2\,V$ and $3\,V$ in first $1/3$ of distance $S$, second $1/3$ of $S$ and third $1/3$ of $S$ respectively. Its average speed will be :-
A car runs at a constant speed on a circular track of radius $100\,m$ , taking $62.8\,sec$ for every circular lap. The average velocity and average speed for each circular lap respectively is
Velocity of an object in rectilinear motion is given as function of time by $v = t -t^3$, where $v$ is in $m/s$ and $t$ is in seconds. Its average velocity over the time interval from $t = 0\ s$ to $t = 2\ s$ is........$m/s$