When a force is exerted on an item that remains constant across time, it is called a constant force. A constant force assists in maintaining an object’s constant speed and enables an object to move uniformly. Similarly, a force exerted on a stationary item is said to be continuous if it contributes to the object’s equilibrium maintenance. In other terms, a constant force is a force that continues to act on an object indefinitely long as the physical conditions are constant. In the following article, we will learn about constant and variable forces and a few examples.

Difference between constant and variable force:

Constant and variable force can be defined in the following ways:

• If the force acting on a body is variable (changes over time), it is referred to as variable force. When a varied force is applied to a body, the body’s motion is accelerated unevenly.
• When the force acting on a body remains constant across time (i.e., the same level of force), the force is said to be constant.
• When a constant force is applied to a body, the body’s motion accelerates uniformly.

How do constant and non-constant forces differ?

• Variable force arises when the direction and magnitude of a force change as a body moves. Variable forces include magnetic force, spring force, and electrostatic force. This is a major difference between constant and non-constant force or variable force. 
• The vast majority of forces encountered in daily life are variable forces. The work performed by a variable force can be calculated by dividing displacement into tiny intervals.
• When a force removes a thing and exerts a force on it, the force may alter the direction, magnitude, or both of the object’s dimensions. These are referred to as variable forces. 
• Calculating the work performed by a variable force is slightly more complicated than computing the work performed by a constant force. 
• By dividing displacement into small intervals, the work performed by a variable force can be computed. The differential work performed in this tiny interval is calculated and integrated over the entire displacement to obtain total work.

Example of constant force:

There are several constant force examples that we will go through here, which will help you understand how constant and variable forces differ from each other.

Gravitation:

• The gravitational force attracts all objects on the earth’s surface. The magnitude/intensity with which an object is drawn to the earth adds to the object’s weight. 
• The weight remains constant regardless of time fluctuation, i.e., it is constant. 
• In other words, gravity works on an object regardless of its position in time, which is why it is classified as a constant force.

Frictional Force

• The frictional force is applied in reaction to an object’s motion. It frequently acts in opposition to the movement of that particular body. 
• The friction applied to a specific object is not time-dependent. 
• The friction intensity is maintained at a constant value at each instant of time. Thus, friction is a well-known example of constant force.

Upthrust:

• The upthrust or rising force is the force that a fluid exerts on a body that it comes into contact with. For example, the force applied by the water on the surface of the boat is uniform and independent of time. 
• As long as the object remains in contact with the fluid, it experiences buoyancy; also, there is no change in the intensity of the force exerted by it. 
• As a result, upthrust is an invariant force and is a key example to understanding the difference between constant and non-constant force.

Pendulum:

• A pendulum oscillates back and forth indefinitely until the energy contained inside it runs out.
•  To maintain a pendulum’s continuous movement, it must be supplied with a steady force.
• This is a good example of constant force as it can be generated by either pushing the pendulum or constructing an artificial setup.

Holding something:

• Because no displacement occurs when an object is held in a stationary position, the labour required to maintain the object’s stationary position is negligible.
• Nonetheless, it requires a significant amount of force to maintain the object’s stationary position. 
• In nature, this force must be consistent; otherwise, the item loses its state of rest and begins to demonstrate motion. This is where constant and variable force differs.

Cycling:

• Cycling is an excellent demonstration of how constant force exists. A large amount of mechanical force is necessary to keep a bicycle moving. 
• To maintain the bicycle’s persistent pace, it must be supplied with a constant force that does not fluctuate with time or distance. 
• Thus, the force that keeps the bicycle going at the same speed throughout the voyage is referred to as a constant force. This is another example of the difference between constant and variable force.

Hydrostatic Pressure:

• The hydrostatic force is the force that a fluid exerts on the outside of a submerged body.
• It has a proclivity to act on an object as long as it is suspended in the fluid. 
• It is not time-dependent, which is why it is continuous in nature. As a result, hydrostatic force is constant.

Force Between Molecules/Within Molecules:

• Intermolecular force and intramolecular force, respectively, are the forces that occur between the molecules of a compound or between the molecules of two separate compounds. 
• These forces tend to keep the compounds stable. These forces do neither wane nor get stronger over time. 
• Due to their invariance with respect to time, these forces are classified as constant forces.

Conclusion:

Herein, we have learned about the basics of constant force. The concept of constant force is described as a force exerted at a time that remains uniform, and thus it enables the object to remain uniformly. The key difference between constant and variable force is that the force applied to a body acts unevenly in the case of a variable force. This way, it does not stay uniform. Some examples of constant force are gravitation, upthrust, hydraulic pressure, pendulum, cycling, etc., where the force is applied consistently throughout the object at a uniform rate.