An object moves with speed $v_1, v_2$, and $v_3$ along a line segment $A B, B C$ and $C D$ respectively as shown in figure. Where $AB = BC$ and $AD =3 AB$, then average speed of the object will be :

A motor cyclist travels a certain distance with a uniform speed of $30\, m/s$ and immediately turns back and returns to starting point with a uniform speed $20\, m/s$. Then the average speed of the motor cycle is ..........$m/s$ :-

Between the two stations a train accelerates uniformly at first, then moves with constant velocity and finally retards uniformly. If the ratio of the time taken be $1 : 8 : 1$ and the maximum speed attained be $60\,km/h,$ then what is the average speed over the whole journey.......$km/h$

A point moves with uniform acceleration and ${v_1},\,{v_2}$ and ${v_3}$ denote the average velocities in the three successive intervals of time ${t_1},\,{t_2}$ and ${t_3}$. Which of the following relations is correct

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

A particle moving in a straight line covers half the distance with speed of $3 \,m/s$. The other half of the distance is covered in two equal time intervals with speed of $4.5 \,m/s$ and $7.5 \,m/s$ respectively. The average speed of the particle during this motion is...... $\,m/s$