Question

2. Which of the following are not correct?
The basic unit of time is second.
(ii) Every object moves with a constant speed.
(iii) Distances between two cities are measured in kilometres.
The time period of a given pendulum is constant.
(v) The speed of a train is expressed in m/h.
(iv)​

Answer 1

We know that,

(i) The basic unit of time is second, second is the SI unit of time.

(ii) Every object may or may not moves with a constant speed. Some are accelerating also.

(iii) The Distance between two cities are measured in kilometers. it is big unit of distance.

(iv) The time period of a given pendulum is always constant because it depends on the length of the pendulum.

(v) The speed of a train is measured in km/h and in m/s.

Hence, This is the correct answer.