A body moves in a straight line for time $t_1$ with velocity $v_1$ and for time $t_2$ with velocity $v_2$ in the same direction. If the average velocity is equal to $(2v_1v_2)/(v_1+v_2)$, then the condition relating $t_1$ and $t_2$ is:

A particle moves for 20 seconds with velocity 3 m/s and then velocity 4 m/s for another 20 seconds and finally moves with velocity 5 m/s for next 20 seconds. What is the average velocity of the particle in m/s is

Two trains are moving with equal speed in opposite directions along two parallel railway tracks.

If the wind is blowing with speed ‘u’ along the track so that the relative velocities of the trains with respect to the wind are in the ratio $1:2$ then the speed of each train must be

A car travels for a time $t$ with speed $v$ and then for an equal time $t$ with speed $3v$. What is the average speed of the car?

A particle undergoing simple harmonic motion has an amplitude $A$ and angular frequency $\omega$. What is its average speed over one complete oscillation?

A car travels 20 km east and then 10 km west in 2 hours. What is its average speed?

The displacement of the particle varies with time according to the relation $x = \frac{k}{b}\left[ {1 - {e^{ - bt}}} \right].$ Then the velocity of the particle is

A particle is moving with a constant speed v in a circle. What is the magnitude of average after half rotation?

An object moves with a velocity of 5 m/s for 10 seconds and then with a velocity of -5 m/s for another 10 seconds. What is its average velocity over the entire 20 seconds?

A car travels from point A to point B with a speed of 40 km/h and returns from B to A with a speed of 60 km/h. What is its average speed for the entire journey?

If a body covers first half of its journey with uniform speed ${V_1}$ and the second half of the journey with uniform speed ${V_2}$ then the average speed is