## Newton First Law of Motion – Class 11 | Chapter – 5 | Physics Short Notes Series PDF for NEET & JEE

Newton First Law of Motion: Newton’s First Law of Motion, also known as the Law of Inertia, states that an object at rest will remain at rest, and an object in motion will continue in a straight line at a constant speed, unless acted upon by an unbalanced force. This law explains that objects will maintain their state of motion, whether at rest or in motion, unless an external force is applied to change that motion. The tendency of an object to resist changes in its motion is called inertia.

There are two conditions on which the 1st law of motion is dependent:

• Objects at rest: When an object is at rest, velocity (v = 0) and acceleration (a = 0) are zero. Therefore, the object continues to be at rest.
• Objects in motion: When an object is in motion, velocity is not equal to zero (v ≠ 0), while acceleration (a = 0) is equal to zero. Therefore, the object will continue to be in motion with constant velocity and in the same direction.

## Characteristics of Newton First Law of Motion

The characteristics of Newton First Law of Motion, also known as the Law of Inertia, include:

• Objects at rest remain at rest: An object at rest will remain at rest, and will not move until an external force is applied to it.
• Objects in motion stay in motion: An object in motion will continue to move in a straight line at a constant speed, unless acted upon by an external force.
• Constant velocity: An object in motion will maintain a constant velocity (speed and direction) unless acted upon by an external force.
• Inertia: The tendency of an object to resist changes in its motion is called inertia. An object with a greater mass will have more inertia and require more force to change its motion.
• Unbalanced forces: An object will only change its state of motion if an unbalanced force is applied to it. Balanced forces will not change the state of motion of an object.
• Frame of reference: The motion of an object is described relative to a particular frame of reference, which can be stationary or in motion.

## Applications of Newton First Law of Motion

The Newton First Law of Motion, also known as the Law of Inertia, has numerous applications in different fields. Some of the applications of Newton’s First Law of Motion are:

• Safety: The Newton First Law of Motion is used in designing safety features in cars, airplanes, and other modes of transportation. Seat belts, airbags, and crumple zones in cars are designed to reduce the effects of inertia during sudden stops or collisions.
• Sports: The Newton First Law of Motion is applied in various sports activities such as football, soccer, and baseball. A ball in motion will continue moving in the same direction until an unbalanced force, such as a collision with a player or a wall, changes its motion.
• Space exploration: The First Law of Motion is used in the design of spacecraft and their trajectories. Once a spacecraft is launched, it will continue to move in a straight line at a constant speed, unless acted upon by an external force such as gravity or a rocket engine.
• Physics experiments: The First Law of Motion is used in physics experiments to study the behavior of objects in motion. For example, a ball rolling on a flat surface can be used to study friction and the effect of different types of surfaces on the motion of objects.
• Manufacturing and engineering: The First Law of Motion is used in the manufacturing and engineering of machines and equipment. The design of engines, turbines, and other equipment takes into account the principles of the First Law of Motion to ensure that the equipment functions properly and safely.

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