You have a bag of cotton and an iron bar, each indicating a mass of $100\, kg$ when measured on a weighing machine. In reality, one is heavier than other. Can you say which one is heavier and why?
The bag of cotton is heavier than iron bar. This is because the surface area of the cotton bag is larger than the iron bar. Hence, more buoyant force acts on the bag than that on an iron bar. This makes the cotton bag lighter than its actual value. For this reason, the iron bar and the bag of cotton show the same mass on the weighing machine, but actually the mass of the cotton bag is more than that of the iron bar.
How does the force$(F)$ of gravitation between two objects change when the distance between them is reduced to half ?
State the universal law of gravitation.
You find your mass to be $42\, kg$ on a weighing machine. Is your mass more or less than $42\, kg$?
Why is the weight of an object on the moon $\frac {1}{6}^{th}$ its weight on the earth?
The earth and the moon are attracted to each other by gravitational force. Does the earth attract the moon with a force that is greater or smaller or the same as the force with which the moon attracts the earth? Why?