Question

There are three solids made up of aluminium, steel and wood of the same shape and same volume. Which of them would have highest inertia? Give reason for your answer.

Answer 1

Hint: The resistance to change in motion of an object is known as inertia. The inertia of an object is mass dependent. The objects with large mass have high inertia and the lighter objects have low inertia. Inertia is basically dependent on the first law of motion.

Complete step by step answer:
Inertia is nothing but the resistance created by the object itself to the change in velocity. Inertia is dependent on mass or we can say it is directly proportional to mass. Heavier bodies have more resistance towards change in their velocity or speed and direction. The other definition for the inertia can be that it is the tendency of objects to keep moving in a straight line with a constant speed or in simpler words we can say resistance to change in motion of objects. The term inertia is directly related to the first law of motion given by Isaac Newton. The first law of motion says that the object moves with constant velocity if any external force is not applied to it. The external force will change the direction and speed of the particles or objects. Hence the inertia is derived from the first law of motion.
We have three solids made up of aluminium, steel and wood and the mass of these three solids will depend on their density because the volume of all these solids is the same. And we know that \[{\text{density = }}\dfrac{{{\text{mass}}}}{{{\text{volume}}}}\] . Therefore density is directly proportional to the mass of solid. The steel has the highest density, so steel has the maximum mass among all of these, hence the steel has the highest inertia.

Note:
 An object falling under the influence of gravity has also inertia. The falling object tries to keep its velocity the same but the gravitational force attracts and changes its velocity while the air resistance also plays an important role in the inertia of free falling objects. If the speed of the object is low then the air resistance will be negligible.