Explain Inertia and mass...?

Question

i've missed a couple of science lessons.

i need to know what Inertia is.

I've got a basic Idea but it is still hard for me to understand it all.

I know it's Newton's first law.

"if an object is at rest it will stay at rest, if an object is moving in a straight line it will continue to do so, unless acted on by an unbalanced force."

What has more Inertia...?

Examples like this would be helpful (and can you answer this as well?)

a 50kg man moving at 10 metres a second, or, a 120kg man standing still?

(work out the mass or something...a formula or just a simple answer will be great)

Answer 1

When an object is at rest, then it continues to be in rest. If it is moving, then it continues to be moving in the same direction with the same speed. This is called state of the system. When the object is at rest and it starts moving, then it is said that it changed its state. If it is moving and if it comes to rest or changes speed or changes direction or any combination of these, then also it is said to have changed state.

You need to apply force on an object if you want the object to change its state. Any object tries to resist change.

This resistance against external force is called as inertia. Mass is a quantitative way of measuring inertia.

In the given example 120kg standing still has more inertia because he has more mass.

See the source that I have cited to understand Newton's first law in more detail.

Answer 2

Inertia is dependence of mass. So the man's speed is not a limiting factor in this case. Comparing their masses, the 120 kg man has more inertia.

There are 2 statements that summarize it.

1. The greater the mass of an object, the more difficult it is to start/stop it.

2. The greater the mass of the body, the greater ite inertia.

Some questions that will set you thinking.

1) Why do we jerk forward when the bus stops?

Ans: When the bus suddenly stops, we are still moving in the forward direction due to inertia.(Remember that inertia is the reluctance of an object to change its line of motion/state of rest?)

2) Why is it dangerous for lorries to go against the speed limit?

Ans: Because they have a larger mass, they have a higher inertia. Hence they find it more difficult to stop/brake in time.

I hope you find these useful.

Answer 3

Inertia is a tendency of an object to resist change in its state of motion. More massive objects have more inertia; that is, they have more tendency to resist changes in the way they are moving.

The 120kg man has more inertia because he has more mass than the 50kg man.