Q: What is the SI unit of density?

Density is mass per unit volume ($\text{Density} = \frac{\text{Mass}}{\text{Volume}}$). The SI unit of mass is $\text{kg}$ and volume is $\text{m}^3$, so the unit of density is $\text{kg/m}^3$.

Question 1

If the distance between two objects is doubled, the gravitational force between them becomes:

Accepted Answer

According to the universal law of gravitation, $F \propto \frac{1}{d^2}$. If distance $d$ becomes $2d$, the force becomes $\frac{1}{(2)^2} = \frac{1}{4}$ of the original force.

Question 2

The weight of an object on the Moon is approximately how much of its weight on the Earth?

Accepted Answer

The acceleration due to gravity on the Moon is about $1/6$th of that on Earth. Therefore, the weight of an object on the Moon is $\frac{1}{6}$th of its weight on the Earth.

Question 3

Which of the following quantity remains constant everywhere in the universe?

Accepted Answer

Mass of an object remains constant everywhere because it is the measure of the quantity of matter contained in it. Weight changes with acceleration due to gravity.

Question 4

What is the direction of the buoyant force acting on an object immersed in a liquid?

Accepted Answer

Buoyancy is an upward force exerted by a fluid that opposes the weight of a partially or fully immersed object. Hence, its direction is vertically upwards.

Question 5

What is the SI unit of density?

Accepted Answer

Density is mass per unit volume ($	ext{Density} = \frac{	ext{Mass}}{	ext{Volume}}$). The SI unit of mass is $	ext{kg}$ and volume is $	ext{m}^3$, so the unit of density is $	ext{kg/m}^3$.

Gravitation