Answer: Option A. -> True
:
A

The slope of a displacement-time graph gives us thevelocity. Theslope at any point in a curve can be found by drawing a tangent on it. In the figure, a tangent has been drawn at point A.
$\text{Slope}=\frac{\text{Change in y-coordinate}}{\text{Change in x-coordinate}}$
At point A, clearly, there is no change in the y-coordinate. Hence, the slope is zero. This implies that the velocity at point A is zero.

Answer: Option C. -> 625 m
:
C
Given,
initial velocity, $u=90kmph$ = $90\times \frac{5}{18}$ $=25m{s}^{-1}$
acceleration, $a=–0.5m{s}^{-2}$
final velocity, $v=0$ (brakes are applied)
Let 's' be the distance travelled.
From the third equation of motion,
$v^2=u^2+2as$
$0={25}^2+(2\times -0.5\times s)$
$\Rightarrow s=625m$
Hence the distance covered is $625m$.

Answer: Option B. -> 4400 m, 400 m
:
B
Given:
Diameter of the circle, $d=400m$
Time taken to complete one circle, $T=40s$
Total time of motion, $T_2=2min20s$
Circumference of circle, $C=\pi d$
Speed is defined as the ratio of distance covered to time taken.
Hence, speed of the runner
$v=\frac{C}{T}=\frac{\pi d}{T}$
Total time of motion, $T_2=2min20s=140s$
Total distance covered is given by:
$D=v{T}_2$
$D=\pi d\frac{T_2}{T}$
$D=\pi \times 400\times \frac{140}{40}$
$D\approx 4400m$
No. of rounds completed:
$n=\frac{\text{Total distance covered}}{\text{Circumference of the circle}}$
$n=\frac{D}{\pi d}$
$n=\frac{T_2}{T}$
$n=\frac{1400}{40}=3.5$
This means that he will be at the diametrically opposite end, i.e., he starts at A and ends at B.
Hence displacement, $s=2r=400m$

Answer: Option B. -> Uniform motion
:
B
Uniform motionis when object covers equal distances in equal intervals of time in the same direction.
In this case, the boy covers equal distances in equal intervals of time because his speed does not change.
Also, his direction does not change.
Therefore, the motion of the boy is an example for uniform motion.

Answer: Option B. -> 0.8 ms−2
:
B
Given:
Initial velocity,$u=0m{s}^{-1}$
Final velocity, $v=20m{s}^{-1}$
Time, $t=25s$
From the first equation of motion,
$v=u+at$,
$20=0+a\times 25$
$\Rightarrow a=\frac{20}{25}=0.8m{s}^{-2}$

Answer: Option B. -> 125 m
:
B
Given, final velocity, $v=0$, acceleration,$a=-10m{s}^{-2}$, time taken, $t=5s$.
Let the initial velocity be $u$.
From the first equation of motion, $v=u+at$,
$0=u+(-10\times 5)$
$\Rightarrow u=50m{s}^{-1}$
From third equation of motion,$v^2$ = $u^2+2as$,
$0={50}^2+2\times -10\times s$
$\Rightarrow s=125m$
Therefore, the truck will stop after $125m$.

Answer: Option A. -> 2.5 cms−2
:
A
The motion is depicted below

Let $u$ be the initial velocity,$v$ be the final velocity and $t$ be the time taken.
$v=15cm{s}^{-1},u=10cm{s}^{-1},t=2s$
We know thatacceleration, $a$ is given by:
$a=\frac{v-u}{t}$
$a=\frac{15-10}{2}$$cm{s}^{-2}$
$a=2.5cm{s}^{-2}$

Answer: Option D. -> along the tangent
:
D
Uniform circular motion is described as the motion of an object in a circle at a constant speed. As an object moves in a circle, it is constantly changing its direction. At all instances, the object is moving tangent to the circle. Since the direction of the velocity is the same as the direction of the object's motion, the velocity is directed tangent to the circle as well.

Answer: Option B. -> The average velocity is zero.
:
B
The average speed is given by the ratio of the total distance travelled to the total time taken.
During a round trip,
The total distance travelled = length of the path $\ne 0$
$\therefore$ the average speed $\ne 0$
Also, the object comes back to the same point from where it has started the journey. So, the total displacement of the object is zero. The average velocity is given by the ratio of the total displacement to the total time taken.
$\therefore$ the average velocity $=0$
Hence, the average velocity is zero for a round trip.

Answer: Option D. -> Distance = 2πr and displacement = 0
:
D
Distance only depends on the magnitude and is equal to thetotal path covered.
Here, distance = perimeter of the circular track =2πr
Displacement depends on both magnitude and direction.
It depends only on the initial and final positions of the body and when you join initial and final points with astraight line, it gives thedisplacement of the body.
Here initial and final positions are the same, hence displacement is zero.