Question

Which of the following distance-time graphs shows a car moving with speed which is constant?

(i)
(ii)
(iii)
(iv)

• A. (i), (ii), (iii), and (iv)
• B. (i), (ii), and (iv) only
• C. (ii) only
• D. (i) and (iv) only

Answer 1

The correct option is D (i) and (iv) only

Speed is constant when an object covers equal distance in equal interval of time.
The graph having horizontal line represents that the object is at rest as the distance is not changing at all.
In the curved graph, unequal distance is travelled in equal intervals of time. Hence, the car is not moving with a constant speed in this case. This is a case of non-uniform motion.
The other two graphs((i) and (iv)) having a straight line represents constant non-zero speed as equal distance is covered in equal interval of time. Hence, case (i) and case (iv) represents constant speed.