 # Laws of Motion in Real Life

## Understanding Newton’s First Law

The first law of motion, as formulated by Newton states that an object at rest will remain at rest and an object in motion will stay in motion, at a constant velocity unless or until outside forces act upon it. Examples of the first law in life are various.

One of the best associations of Newton’s first law of motion can be made with an automobile. A motorbike riding along the highway remains in motion unless some external force acts upon the velocity.

The latter term (velocity), though it is generally comprehended to be the same as speed, is, in fact, more distinct: velocity can be defined as the speed of an object in a particular direction. Everything inside a van moving at a velocity, say 50 km/hr moves forward at the same rate. If the same car runs into a tree, the motion will be stopped abruptly. In spite of the motion being stopped after the crash, the car still responds to inertia. During this period of time, rather than bouncing off the brick wall, it continues ploughing into it.

From the above scenario, it would be wrong to conclude that inertia is harmful. In the familiar magic stunt, where the full table setting placed on a table is whisked out of the tablecloth from under the dishes, without upsetting so much as glass, makes use of inertia to its advantage. This trick might seem like real magic to most, but under the right conditions, it can be performed by anyone.

To make the trick work, several things must be aligned. The person executing the trick must be skilled and practised. It is best to reduce the friction between the cloth and settings on the one hand, and the cloth and table on the other, as a physical consideration. Objects are more resistant to the motion when the mass of the table set is maximised. Maximising the mass of the table settings makes the objects more resistant to the movement. Hence, inertia—which is measured by mass—plays a crucial role in making the tablecloth trick work.

## Describing Newton’s Second Law

The first law of motion describes the effect of motion on velocity, while Newton’s second law quantifies the force necessary to cause that change. The second law states that the net force acting upon an object is a product of its mass multiplied by its acceleration. Acceleration is defined as a change in velocity over a given time interval: hence, acceleration is expressed in terms of “feet (or meters) per second per second”—that is, feet or meters per second squared. The second law develops the first law by describing the force necessary to change the velocity of an object. The second law helps us calculate the force needed to move an object, and thus people put it into use every day without knowing that they are doing so.

## Defining Newton’s Third Law

Newton’s third law predicts what would happen when one force interacts with another force. Newton’s third law states that every action has an equal and opposite reaction. Unlike the second law, the third law is much easier to experience in daily life. One of the examples of the third law of motion is of a book sitting on a table. The book sitting on a table exerts a force equal to its mass multiplied by its rate of acceleration. The force of gravity tries to accelerate the book towards the centre of the Earth. The table exerts an upward force on the book to prevent it from acceleration.