$A$ particle moving in a straight line covers half the distance with speed $6 \, m/s$. The other half is covered in two equal time intervals with speeds $9 \, m/s$ and $15 \, m/s$ respectively. The average speed of the particle during the motion is: (in $ \, m/s$)

$A$ charged object is launched inside a time-varying electric field. Its motion is recorded by a video camera on a video tape. When it is at a certain moment $A$,its position vector $\vec{r}$,velocity $\vec{v}$,and acceleration $\vec{a}$ are measured. $A$ student watches the video at a later time but mistakenly plays the tape in the reverse direction. What are the position,velocity,and acceleration of the object at moment $A$ observed by the student,respectively?

The displacement of a particle moving in a straight line depends on time as $x = \alpha t^3 + \beta t^2 + \gamma t + \delta$. The ratio of initial acceleration to its initial velocity depends on:

$A$ parachutist drops freely from an aeroplane for $10\,s$ before the parachute opens. Then he descends with a net retardation of $2.5\,m/s^2$. If he bails out of the plane at a height of $2495\,m$ and $g = 10\,m/s^2$,his velocity on reaching the ground will be .......$m/s$.

The speed-time graph for a body moving along a straight line is shown in the figure. The average acceleration of the body may be .......... $m/s^2$.

State whether the following statements are true or false:
$(a)$ Velocity can change without a change in speed.
$(b)$ The total distance covered by a freely falling body in a given time is directly proportional to the time.
$(c)$ $A$ particle is a point object that possesses dimensions.