Force and Acceleration

Definition of Force and Acceleration

Force is an agent acting externally and is capable of changing the state of rest or motion of a particular body. It is also defined as the push or pull on an object which has a certain mass and causes the object to change its velocity.

Acceleration is often used to describe a state when speed increases but in Physics, acceleration is the rate of change of velocity with time. Any change in the velocity of an object results in an acceleration: increasing speed as well as decreasing speed (deceleration or retardation), or changing direction (centripetal acceleration).

Units of Force and Acceleration

The direction towards which the force is applied is called the direction of the force, and the application of force is the point where force is applied. Force can be measured by using a spring balance. The SI unit of force is Newton(N). Its dimension is LMT-2. We denote force with the letter 'F'.


Calculating acceleration is dividing velocity by time — or in terms of SI units, it is dividing the meter per second [m/s] by the second [s]. Dividing distance by the time twice is the same as the dividing distance by the square of time. Therefore the SI unit of acceleration is meter per second squared (m/s2). Acceleration is denoted with 'a'.

Relationship between Force and Acceleration

The relationship between force and acceleration is shown by the equation F=ma, where “F” stands for force, m stands for mass, and a stands for acceleration. Force is a push or pulls that an object exerts on other objects. Acceleration is the rate of change of the speed of an object, so if an object has mass, and it is accelerating through space, then the object is said to exert a force. This principle is described by Newton’s second law of motion.


According to Newton's first law, we know that a body will continue to be in a state of rest or uniform motion until an external force acts on it. Force can be described as an interaction that changes the state of a body that is from a state of rest to the state of motion or vice-versa. We must notice that the law says net force should act on the body. So we will see what that actually means by considering the following situation -


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Here, one force is acting towards the right and an equal and opposite force is acting towards left hence the net force on the body is zero so the body. So, if a force is acting on a body that does not mean that the state of the body will have to change, it may or it may not. Some known forces are frictional force, gravitational force, normal force, etc.


If a net force acts on the body then the velocity of the body either increases or decreases. Thus, this rate of change of velocity of the body is acceleration. We also observe that the greater the force the greater be its acceleration. So there has to be some relation between force and acceleration.

F = ma

Where,


F=force

m=mass 

a=acceleration


From this relation, it is understood that acceleration not only depends on the force applied to it but also on the mass of the body on which it is applied. If the same force is applied to two different bodies then the one with a smaller mass will have greater acceleration. This was just an introduction to force and acceleration. So the rate of change of velocity of a body is nothing but it's acceleration. We also observe that the greater the force the greater the acceleration. Hence, there must be some relation between force and acceleration. This is what is given by Newton's Second Law.

Fun Facts

  • Sir Isaac Newton was the first scientist to study gravity and force. His three laws are still used by scientists even today.

  • Force was described by Isaac Newton in his law called Newton’s second law of motion.

  • Any kind of force is just a push or a pull in reality.

  • Magnetism is a type of force. An object might be pulled by a magnet towards it or be pushed away.

  • Inertia is not a force.

  • Torque is a kind of force that rotates or twists the objects.

  • Gravitational and electromagnetic forces don’t need to have contact with the object for exerting force. They can exert a force on objects which are away from them.

  • Objects with acceleration can’t reach the infinite velocity. The fastest possible velocity is the velocity of light, which is around 299,792,458 m/s.

  • Acceleration is produced by the force on an object.

  • Negative acceleration is also known as retardation.

FAQ (Frequently Asked Questions)

1. What is the difference between Force and Acceleration?

Force is said to be equal to the change in momentum per change in time. For a constant mass, the force equals mass times acceleration. In mathematical form, F = ma (where, F=force, m=mass, a=acceleration). If the force is doubled, the acceleration will also be doubled, but if the mass is doubled, the acceleration is cut into half. The relationship between force and acceleration can be described from Newton's First Law. If the force applied to an object is increased, then the acceleration of that object also increases by the same factor. In short, force equals mass times acceleration.

2. What is the gravitational force?

The gravitational force is a force that attracts any two objects with mass. The gravitational force is called attractive because it always tries to pull masses together, it never pushes them apart. In fact, every object is pulling on every other object in the entire universe. This phenomenon is also known as Newton's Universal Law of Gravitation. Admittedly, we don't have a very large mass and so, we are not pulling on those other objects much. Objects which are really far apart from each other don't pull on each other noticeably either. But the force is there and so we can calculate it.