Law of inertia
Inertia is a measure of a body. The greater the mass
of a body greater its inertia or vice versa when any vehicle starts
suddenly, the passenger falls backwards. It is due to the inertia property of the
body.
The persistence of all matter to remain at rest when left
alone or to keep in motion after being acted on by an outside force is called
inertia. Inertia is a definite characteristic of all matter whether solid,
liquid, or gas. Newton’s first law may now be restated as follows:
Everybody persists in a
state of rest or of uniform motion in a straight line, unless compelled by some
outside force to change that state.
Since mass is the resistance to motion in a body, it follows
that the more mass a body has the more inertia it will have. You cannot start a
freight car moving all by yourself because you cannot produce the force
necessary to overcome its huge inertia.
If some powerful force
starts this car and lets it roll along the tracks by itself, you won’t be able
to stop it immediately by yourself because its persistence to keep in motion is
just as great as its persistence to remain at rest, and it will take as much
outside force to stop it as it did to start it. The car will eventually stop
because of the friction of the wheels on the track and the rubbing of the axles
against the car.
Some other examples of
moment of inertia
If you want your automobile to stop suddenly you don’t merely
shut off the gas and let the car roll along until it comes to rest. You apply
the brakes, and the tight brake bands, rubbing against the wheels of the car,
produce sufficient friction to overcome the momentum of the car and quickly
bring it to a stop.
The same is true of a railroad train. When the air brakes are
applied to all the cars friction soon overcomes the inertia of the massive train
and brings it to a stop.
If you happen to be standing in one of the cars and
the brakes are applied very suddenly, you will fall forward. This is because
your body is going with the speed of the train and your feet are in contact
with the floor of the car.
When the car slows up suddenly, your feet do the
same, but the rest of your body cannot keep up with your feet and consequently
keeps on moving forward.
One of the most dramatic uses of this effect is in the
accelerator, an instrument that employs inertia to measure linear motion,
and is vital in the inertial navigation systems that now guide aircraft,
rockets, and ships.
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science