Which of the following are not correct? (i) The basic unit of time is second. (ii) Every object moves with a constant speed. (iii) Distances between two cities are measured in kilometres. (iv) The time period of a given pendulum is constant. (v) The speed of a train is expressed in m/h.
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. So, we can say that, (ii), (iv) and (v) are not correct statements. Hence, This is the correct answer.
