Newton’s first law of motion states that an object continues to maintain its state of rest or motion unless or until it is acted upon by an external force. It is also known as the law of inertia. As per the statement of the first law of motion, two types of inertia exist in nature, namely, the inertia of rest and inertia of motion. Inertia is the natural tendency of a body to resist change in its state. It is proportional to the mass of the object, which means greater be the mass, greater is the inertia possessed by the body and vice-versa. The laws of motion were discovered in the year 1687 by an English mathematician, physicist, astronomer, theologian, and author, Sir Issac Newton. The laws of motion are mentioned in one of the books written by him called Philosophiae Naturalis Principia Mathematica, commonly known as the Principia. In simple words, the first law of motion states that an object at rest stays at rest and an object in motion continues to exhibit motion, provided no force acts on the object from the outside.
Examples of Newton’s First Law of Motion
1. Brakes applied by a Bus Driver Abruptly
While travelling on a bus, when the bus driver abruptly applies the breaks, we tend to feel a momentary pull in the forward direction. The reason behind this jerk felt by the passengers sitting inside the bus is the law of inertia. Due to the inertia of motion, our body continues to maintain a state of motion even after the bus stops, thereby pushing us in the forward direction.
2. An Object Placed on a Plane Surface
One of the finest examples of Newton’s first law of motion is an object that is simply placed on the surface of the earth. The natural tendency of the object is to maintain its state of rest until a force acts on it. For instance, a book kept on a bookshelf does not change its shape, size, or position until acted upon by an external force.
3. Marathoner Running beyond Finish Line
A marathon runner is not able to stop himself right after crossing the finish line. He/She tends to take time and cover a few meters of distance running beyond the finish line. This is because the inertia of motion or Newton’s first law of motion resists a sudden termination of motion and compels the body to maintain its state of motion.
4. A Ball Rolling on the Ground
As per Newton’s first law of motion, a ball rolling on the ground tends to maintain its state of motion till infinity, if no external force acts on it; however, the force of friction acting on the ball from the outside helps to break the motion of the ball and brings it to rest.
5. An Object Thrown in Outer Space
If an object is thrown in outer space, it tends to move in a direction to infinity. This is because outer space lacks environment, air, and the force of gravity. Hence, the object does not receive any resistance to the motion; therefore, it continues to exhibit motion until it hits a celestial body, strikes a meteorite, or enters the gravitational field of a planet, thereby demonstrating the first law of motion in real life.
6. Washing Machine Dryer
A washing machine dryer entirely works upon the principle of the law of inertia. To dry the clothes, the drum of the washing machine dryer is subjected to motion, which further causes the clothes to move; however, the water molecules contained in the cloth do not follow the motion and stay at their position of rest. Due to the gravitational pull of the earth, the water gets collected at the base of the drum. The holes of the drum let the water out, leaving the clothes dry.
7. Dusting a Carpet
To remove the dust particles from a carpet, it is hanged on a wire and a piece of the stick is used to hit the carpet repeatedly. This induces motion in the carpet, whereas the dust particles continue to maintain their state of rest. When the carpet moves back, the dust particles get carried away with air or fall to the ground due to gravity, thereby demonstrating the law of inertia.
8. Shaking a Tree
When the branch of a tree is vigorously shaken with the help of an external force, it comes to motion; however, the leaves attached to the branch do not comprehend the motion and tend to maintain their state of rest. The motion of the branch of the tree and the inertia of rest exhibited by the leaves cause the shedding of leaves.
9. The Jerk when a Vehicle Starts
When a vehicle starts suddenly, a jerk is felt by the passengers and the drivers sitting inside the vehicle that pulls them backwards. This is because the car comes in motion, but the body continues to sustain its state of rest, thereby leading to a sudden and momentary change in the state known as a jerk.
10. Athlete taking a Short Run before Long/High Jump
An athlete takes a short distance run before a long jump or a high jump. This is because by running a short distance, the player prepares his body and sustains motion in it. This helps him to exhibit a smooth jump. A similar demonstration of the inertia of motion can be observed when a bowler takes a small run before throwing a ball.