Physics

# Newton’s second law of motion

Newton’s second law of motion states that the acceleration of an object’s motion is proportional to the force applied to that object in the same direction as the force.

That’s to say. F = ma

Where F is the force applied, m is the mass of the body, and a is the acceleration produced.

What will happen if a body is subjected to several forces at the same time?

If a body is subjected to several forces at the same time, the acceleration produced is proportional to the vector sum of all the individual forces.

The second law can also be represented with respect to the total force and momentum p of the body:

Therefore, Newton’s second law also states that the total force (net force) acting on a body is equal to the rate of change of momentum of the body.

How does momentum affect net force?

The first law of motion states that when an external force exerts an action on an object, the speed of that object changes. Now we are going to study how the acceleration of an object depends on the applied force. Consider the following example: A car at rest does not require much attention when stationary along one side of the road. But the moving car, even at low speed, can kill a person standing in its path. A small mass, like a bullet can kill a person when fired from a gun. From these examples, it is clear that the impact produced by objects depends on their mass and speed. When we combine mass and velocity of an object, we get another quantity called momentum, which was introduced by Newton.

We are going to define the momentum:

Momentum is both direction and amplitude. Its direction is the same as that of the speed. When a force is applied to an object, it changes the speed of the object, which in turn changes its momentum. Thus, it is concluded that the force required to change the momentum of an object depends on the rate at which the time of the pulse is changed The acceleration of a moving object can be calculated by:

When the object begins its movement, its initial speed is zero, v=0

Hence:

from this equation we can find the acceleration of the object:

Learning outcome:

mass

acceleration

strength

amount of movement

Newton’s second law of motion

Let’s try to understand the concept behind Newton’s second law through a simple experiment.

What is E=mc²

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