7 junio, 2024

Net force: what it is, Newton’s first and second law, examples

What is the net force?

The net force It is the sum of all the forces acting on an object. For example, when you kick a soccer ball, the ball takes off and moves through the air. At that moment, there is a net force acting on the ball. As the ball starts to return to the ground and finally comes to rest, there is also a net force acting on the ball.

Newton’s second law says that “when a net force acts on an object, then that object must be accelerated, that is, its speed changes from second to second”.

There can be several forces acting on an object, and when all those forces are added together, the result is what we call the net force acting on the object.

If the net force adds to zero, then the object is not accelerating, so it is moving with a constant velocity. If the net force adds to a non-zero value, then the object is accelerating.

In nature, all forces oppose other forces, such as friction or opposing gravitational forces. The forces can only produce acceleration if they are greater than the total opposing forces.

If a force pushes on an object, but is matched by friction, the object does not accelerate. Similarly, if a force pushes against gravity, but it is less than the gravitational force on an object, it does not accelerate.

For example, if a 15-Newton push on an object is opposed by a 10-Newton force of friction, the object accelerates as if pushed by a net frictionless 5-Newton force.

Second law of Newton

Newton’s first law of motion predicts the behavior of objects for which all existing forces are balanced.

The first law (sometimes called the law of inertia) states that if the forces acting on an object are balanced, then the acceleration of that object will be 0 m/s/s. Objects in equilibrium (the condition where all forces balance) will not accelerate.

According to Newton, an object will only accelerate if there is a net or unbalanced force acting on it. The presence of an unbalanced force will accelerate an object, changing its speed, its direction, or its speed and direction.

Newton’s second law of motion

This law refers to the behavior of objects for which all existing forces are not balanced. The second law states that the acceleration of an object depends on two variables: the net force acting on the object and the mass of the object.

The acceleration of an object depends directly on the net force acting on the object, and inversely on the mass of the object. As the force acting on an object increases, the acceleration of the object increases.

As the mass of an object increases, the object’s acceleration decreases. Newton’s second law of motion can be formally stated as follows:

«The acceleration of an object produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.»

This verbal statement can be expressed in equation form as follows:

A = Fnet / m

The above equation is often rearranged to a more familiar form, as shown below. The net force is equated to the product of the mass multiplied by the acceleration.

Fnet = m • a

The emphasis is always on net force. The acceleration is directly proportional to the net force. The net force is equal to the mass times the acceleration.

Acceleration in the same direction as the net force is an acceleration produced by a net force. It is the net force that is related to the acceleration, the net force is the vector sum of all the forces.

If all the individual forces acting on an object are known, then the net force can be determined.

According to the above equation, a unit of force is equal to a unit of mass multiplied by a unit of acceleration.

By substituting standard metric units for force, mass, and acceleration into the above equation, the following unit equivalence can be written.

1 Newton = 1 kg • m / s2

The definition of the standard metric unit of force is given by the above equation. One Newton is defined as the amount of force required to give a mass of 1 kg and an acceleration of 1 m/s/s.

magnitude and equation

According to Newton’s second law, when an object accelerates, then there must be a net force acting on it. That is, if a net force acts on an object, that object will accelerate.

The magnitude of the net force acting on an object is equal to the mass of the object times the acceleration of the object, as shown in the following formula:

A net force is the remaining force that produces any acceleration of an object when all opposing forces have cancelled.

Opposing forces lessen the effect of acceleration, decreasing the net force of acceleration acting on an object.

If the net force acting on an object is zero, then the object is not accelerating and is in a state we call equilibrium.

When an object is in equilibrium, then two things can be true: either the object is not moving at all, or the object is moving with a constant speed. The formula for balance is shown below:

examples

Consider a hypothetical situation in space. You are doing a spacewalk and you are fixing something in your shuttle. While working on the issue with a wrench, he gets angry and throws the wrench away, what happens?

Once the key leaves your hand it will continue to move with the same velocity it was given when you threw it. This is an example of a zero net force situation. The key will move with the same velocity and will not accelerate in space.

If you throw the same key on Earth, the key will fall to the ground and finally stop. Why did it stop? There is a net force acting on the wrench, causing it to slow down and stop.

In another example, let’s say you are at an ice rink. He takes a hockey puck and slides it across the ice.

Eventually the hockey puck will slow down and stop, even on smooth slippery ice. This is another example of a situation with a non-zero net force.

References

Newton’s Second Law. Retrieved from physicsclassroom.com.
Cárdenas, R. What is Net Force? – Definition, Magnitude & Equations. Retrieved from study.com.
What is net force? Retrieved from reference.com.
Net force. Retrieved from thefreedictionary.com.
Pearson, A. Force and Motion Chapter 5. Retrieved from physics.gsu.edu.

Deja una respuesta

Tu dirección de correo electrónico no será publicada. Los campos obligatorios están marcados con *