Sir Isaac Newton was the one to postulate the three fundamental laws of motion in a book called “Principia Mathematica Philosophiae Naturalis” in 1686. These theories and principles revolutionized science in many ways.
Out of the three laws, the first law is the law of Inertia. This law demonstrates that the body has the tendency to maintain its state of rest or motion. That means the body tends to oppose or resist any kind of change in its existing state. This property of the body is referred to as Inertia.
Law of Inertia
Newton’s first law states that:
If a body is at constant rest or is moving on a straight path at a constant speed, it tends to remain in the same condition. That means, if the body is at rest, it will tend to remain at rest, and if it is in motion, it will continue to move on the same path at the same speed until and unless some external unbalanced force is acted upon it.
Inertia of Motion
We can define Inertia of motion as the property of a body to oppose any kind of change in its state of motion by itself. It is related to mass; that means the more the mass, the more the inertia will be.
Examples of Inertia of Motion
A passenger falls forward when a fast-moving vehicle suddenly stops
Have you ever noticed what happens when you sit in a moving car, bus, train or any other vehicle, and the driver suddenly pulls the brake?
Yes, you feel a sudden jerk which is why you fall forward as soon as the brakes are applied. The phenomenon behind this is Inertia. What happens here is when the driver applies brakes, your lower body stops moving and comes to rest, just like the vehicle. But the upper body continues to move in a forward direction due to the Inertia of motion.
Due to this Inertia of motion, the body feels forward force when the vehicle stops. As a result, we fall forward when the moving vehicle suddenly stops.
The luggage tied to the roof of the vehicle
Generally, luggage is tied to the roof of vehicles with rope. When the moving vehicle stops suddenly, the luggage on the roof may fall off the bus due to the Inertia of motion. This occurs because when the bus stops, it comes to rest, but the luggage resists the change in the state of motion and moves forward, thereby falling off from the bus roof.
Men in space
The astronauts find it more difficult to stop moving in space as the gravity there is very low. So, if they start moving, they keep moving due to the Inertia of motion.
Cause of Concussion
If a player’s head hits the ground while playing a sport like a football, hockey etc., it might lead to a concussion. In reality, the reason behind concussions is the Inertia of motion. The brain inside the skull moves when the player is playing or moving. But as the skull hits the ground, it stops moving, but the brain inside doesn’t. This causes brain injury.
When we slide a hockey puck once, it keeps on sliding across the ice until some external force is applied.
Riding a Bicycle
The bicycle keeps on moving even when you stop peddling until some external force like friction or gravity slows it down.
Swirling of Milk
You might have noticed that the swirling of milk or water continues even after you stop stirring the spoon. This also happens because of the Inertia of motion.
We switch off the electric fan, but it still keeps on rotating; this occurs due to the Inertia of motion.
This is because the blades of the fan are in motion, and they tend to be in motion. Thus, they keep rotating even after the electricity is turned off.
Movement of Satellites
Satellites also move continuously because of this Inertia of motion. This allows the satellites to constantly move forever as there is no external force to stop them.
Car with engine off
A moving car continues to move even when you shut the engine off on a flat surface. It also happens due to Inertia of motion as the moving car wants to keep moving until the frictional force comes into the frame.
While playing with a ball, we see that it keeps rolling for a long time before it finally stops. The Inertia of motion allows the balls to keep rolling until the rolling friction stops it.
While the athletes do long lumps, the Inertia of motion gives them an extra advantage by allowing them to cover a little more distance. And to take this advantage, they need to run before they take a jump.
Marathon & Sprints
In races like marathons or sprints, the athletes continue running even after crossing the finish line. This occurs because they can’t immediately stop due to the Inertia of motion. Thus, they stop gradually by decreasing their speed.
Rotating doors are common in hotels and offices. Once you enter or exit via it, it keeps rotating for several minutes. This is because of the Inertia of motion that makes the door move even when the force is stopped.
In the hammer throw, the athlete has to throw a hammer upto to the longest distance. So before throwing the hammer, they take a few rotations to produce centrifugal force. So, when the athlete releases the hammer, it travels a larger distance because of the Inertia of motion.
The air friction works but is not enough to stop the hammer, and thereby, it is pulled down by the gravitational force.
Landing of an Airplane
The aeroplane doesn’t stop instantly after landing; instead, it keeps moving. If it halts suddenly, the Inertia of motion will throw the passengers in the forward direction.
Thus, the aeroplane travels upto some distance before it comes to a complete halt.
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