Which one of the following statements is not true?

Statement 3 is incorrect because the SI unit of weight is the newton (N), not the kilogram (kg) [3]. Weight is defined as the gravitational force with which the Earth attracts an object [2]. While everyday language often uses kilograms for weight, in science, kilograms are strictly the unit for mass, which represents the quantity of matter [3]. Statement 1 is true as the gravitational force on a 1 kg mass is approximately 9.8 N (F = mg) [2]. Statement 2 is true because, according to Newton's first law, an object moving with uniform velocity on a frictionless surface requires no net force to maintain its motion. Statement 4 is true because momentum (p = mv) for a 100 kg man at 2 m/s is 200 kg·m/s, and the unit kg·m/s is dimensionally equivalent to the newton-second (N·s).

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 5: Exploring Forces > 5.5 Weight and Its Measurement > p. 72
2. [3] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 9: The Amazing World of Solutes, Solvents, and Solutions > A step further > p. 142
3. [2] https://en.wikipedia.org/wiki/Mass_versus_weight