Question

What is happening at D ?

A. Stationary
B. Accelerating
C. Fast steady speed; moving away from starting position
D. Slower steady speed; moving away from starting position

Answer 1

Hint: We need to find the nature of the object D, that is, the speed and how it changes with respect to distance and time. We will be using the formula $\text{speed=}\dfrac{\text{distance}}{\text{time}}$ to analyze the nature of the object. We know that speed varies proportionally to the distance and inversely to the time. Accordingly, we can find the nature of D.

Complete step by step answer:
We need to find the nature of D.
From the figure, the plot is distance vs time. A Distance-time graph shows how far an object has traveled in a given time.
We know that $\text{speed=}\dfrac{\text{distance}}{\text{time}}$ . That is speed varies proportionally to the distance and inversely to the time. That is, as time increases (or decreases), speed decreases (or increases). When distance increases (or decreases), speed increases (or decreases).
From, the figure, D is moving away from the starting point. As time increases, D is moving very fast. We can see that it covers more distance in less time.
The Distance-time graph shows the speed. The speed of D is steady, that is, it does not decrease in between. It keeps on increasing.
Hence the correct option is C.


Note:
 Let us analyze the nature of other objects in the given figure. The speed of A remains uniform or stationary, that is, it does not increase or decrease. B is moving away from the starting point slowly. The object C is increasing its speed exponentially. Object E is reducing its speed and finally reaches zero.