FORCE

FORCE

from Femosky110 on 06/12/2020 01:54 PM

Force
A force is a push or a pull applied to an object as a result of the interaction of the object with another object. Every time there is in interaction involving two objects, there is always a force upon every one of the objects. The force between them ceases to exist when the interaction between them stops. Forces only occur as a result of interaction. Without interaction, there will be no force.

 

In summary forces are classified broadly into two.

1. Contact forces
2. Resultant Forces as a result of a distance action
physics
Contact forces
Contact Forces are types of forces that exist between two interacting objects when they are in close contact with each other. The sub-types and examples of contact forces are listed below:

• Frictional forces

• Tensional forces

• Normal forces

• Air resistance forces and

• Applied forces.

Each category of contact force above will be explained in details in our succeeding lessons.

Resultant Forces from a distance action
These are those types of forces that occur when the two objects that are interacting do not have bodily contact with each other; still they are capable of putting forth a push or a pull in spite of their bodily separation. Examples of these types of forces are:

Gravitational forces
Typical example of gravitational force is the force exerted by the sun and the planets irrespective of the wide spatial distance between them. Even when your feet are not in contact with the ground, there still exists a gravitational force or pull between you and the Earth.

Electric forces
These are another example of resultant forces as a result of interactions from remote positions. Examples of electrical forces are the forces that exist between the protons in the nucleus of an atom and the electrons outside the nucleus of an atom. The proton and electron irrespective of the distance from each other exert an electrical force of attraction or pull towards each other.

Magnetic forces
These are another example of resultant forces from a distance action. For instance, two magnets can put forth a magnetic pull against each other even when they are separated by a few centimeters' distance. We will discuss each one of these forces in details in our subsequent lessons.

Examples of contact and action-at-distance forces are listed in the table below.

Contact Forces Distance Forces
Frictional Force Gravitational Force
Tension Force Electrical Force
Normal Force Magnetic Force
Air Resistance Force
Air Resistance Force
Applied Force
Spring Force
Measurement of Force
The standard unit (SI) of measurement of Force is the Newton. A Newton is shortened as an "N." So when you say "10.0 N", it means 10.0 Newton of force.

One Newton is the amount of force required to give 1-kg mass of an object an acceleration of 1 m/s/s. Thus, we could derive the unit of 1Newton as:

A force is a vector quantity not a scalar quantity. A vector quantity is a quantity that has both magnitude and direction.

To completely explain the force acting upon an object, its magnitude and direction must be described. Therefore, 10 Newton is not a complete picture of the force acting on an object.

On the contrary, when you say 10 Newton downward, it is a complete explanation of the force acting on an object; both in terms of the magnitude (10 Newton) and the direction (downward).

Due to the fact that a force is a vector that has a direction, it is regular practice to characterize forces using diagrams in which a force is represented by an arrow.

The size of the arrow is a reflection of the size/magnitude of the force and the direction of the arrow shows the direction on which the force is acting. These types of diagrams are referred to as free-body diagrams.

We are going to see some of the example for force and calculation involving finding a force that acts on an object or finding each component of a force.

Example 1
What force is required to accelerate an object having a mass of 8 kg at 7 m/s2?
Solution:
Force is represented with the following formula

F = ma where m is mass and a is acceleration.

F = 8 x 7 = 56 N

Example 2
A body of mass – 20kg was hit by a force of 200 N, what will be the acceleration of the body due to the impact of the force.

Solution
F = ma

a = F / m

a = 200 / 20 = 10 ms2

With these examples, you have learned how to calculate the components of force. You should try your hands on the assignments given below. It will help you master force in physics.

Assignment
1) What force is required to accelerate an object having a mass of 64 kg at 2 m/s2?

2) What the mass of an object that accelerates with 2m/s2 when hit by a force of 30N.

Newton's first law of motions
Newton's laws of motion are one of the fundamental laws that gave us a new ways to understand our universe. Newton's first law of motion stated that every object in a state of uniform motion tends to remain in that state of motion unless an external force is applied to it.

By simple explanation it means that an object at rest will always remain at rest expect it is acting by a nonzero external force.

The idea of a nonzero force will bring us back to our previous topic in vector addition. We define a net force as the resultant force obtained when all the forces acting on an object are summed together. Nonzero force can also be regarded as net force.

Newton's first law of motion is quite similar to inertia. Inertia is one of the fundamental concepts used in physics to describe motion of objects and how objects are affected by applied forces.

Understanding inertia also will help you understand to meaning and implementation of Newton's first law of motion.

Inertia is the resistance of any physical object to any change in its state of motion (including a change in direction). In other words, it is the tendency of objects to keep moving in a straight line at constant linear velocity. (Wikipedia)

Newton's Second Law of Motion
The fundamental concept of Newton's second law of motion deals with the relationship between an object mass, the force that acts on the object and its acceleration. It focuses on the velocity of an object when a force acts on an object.

You should remember that we talked about nonzero force when we discussed Newton's first law of motion, imagine if the net force that acts on an object is not zero, the object will experience a change in velocity due to the applied force on the object. This change in velocity is called acceleration.

This implies that there is a linear relation between applied force and acceleration. Increasing the amount of force that acts on an object will increase the acceleration of the object. Since force and acceleration are vector quantities, it means that they have both magnitude and direction. The force and acceleration moves in the same direction.

Let consider the relationship between the applied force on an object and the object itself. If the same amount of force is applied to the object but of different size, the small object will tend to accelerate faster than the bigger object.

We can deduce so far that

Force = mass x acceleration

A simple example to illustrate Newton's second law of motion is shown below.

Diagram
Newton's third law of motion
By now you must have understood the important of laws that Newton described. These laws have redefines our understanding of our universe. We will detail concisely with Newton's third law of motion now.

Newton's third law of motion stated that for every action there is an equal and opposite reaction. Although it sounds simple but we will dive into it and make it even much easier to understand.

Newton's third law of motion emphasis that for every internal force that acts upon an object, there is an opposing force with the same magnitude but in opposite direction at also acts on the object. This implies that an object is not responsible to initiate its own motion. In this case there is no net force.

Newton's third law is predominant in our everyday life.

A typical example of Newton's third law is shown below.

physics
The force of the small object on top of the big object acts in downward direction but that is also a force with the same magnitude but acts in opposite direction. Since the net force is zero, the small object is at rest on top of the big object.

Normal Force
The concept of normal force is quite confusing for most students new to physics. Some people might think that normal force is just like an ordinary force but it is not true. Let's deal with what normal force means in physics.

Normal force is any force coming from the surface and acting at a right angle to the surface.

In some situation, normal force is just the weight of an object that sits on a level surface. Imagine in a case where the object is inclined to a certain angle on a surface of another object, the normal force is equal and opposite to the perpendicular force.

physics
Frictional Force
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and material elements sliding against each other. Friction force always acts in opposite direction to motion and it tends to reduce the net force that acts on an object.

It is important to know that frictional force depends on the material of which an object is made of and also it is affected by normal force.

Frictional force can be defined by this simple equation: Frictional Force = uF

Where u = coefficient of friction and F is the normal force

A simple illustration of frictional force is shown below.

physics
Equilibrium of Forces
As we have discussion in the vectors and scalar topic and also in Newton's first law of motion, equilibrium of forces is the term used to describe an object with a resultant force of zero. A resultant force of zero is when the upward force is equal to the downward force and the rightward force is equal to the leftward force.

Remember that we do mention of this concept when we treated vector addition, you can back the topic to read more about it.

Equilibrium of forces also implies that the net force that acts on an object is equal to zero. The following conditions are the basis for equilibrium of forces

Leftward force = Rightward force

Upward force = downward force

Net torque = 0

Clockwise torques = Anticlockwise torques

When the net force acting on an object is zero it also implies that the acceleration is equal to zero. You should also know that when acceleration is equal to zero, it does not imply that the object is stationary.

When an object is regarded to be in a static equilibrium it means that the object is at rest. Remember also that an object at equilibrium is either at rest or in motion with the same speed and direction.

Equilibrium of force is an important concept in physics and it has found applications in many different areas. One important area where equilibrium of forces is used is in the construction of structures that carry loads. A typical example is in the construction of bridge. This is necessary to make sure that bridges will maintain equilibrium when many vehicles are line up on the bridge.

physics