Force In physics, force is an external agent which when not opposed by a body, changes the state of motion of that body. In simpler terms, it is the mere push or pull influence experienced by an object. A force can either move a body that was initially in rest (or even accelerate a body in motion) or can make a body in motion come to a position of equilibrium (rest). Force is a vector quantity in nature because it is measured in terms of both magnitude and the direction through which it is acting. Its unit is newton (N), and the value of force is generally given by F = ma
- m is the mass of the object on which the force is applied
- a is the acceleration of that object
The force acting on an object is directly proportional to its acceleration and indirectly proportional to the mass of the object, as proven by Newton’s second law of motion. Force can be classified into fundamental forces and non-fundamental forces, which are products of fundamental forces.
- Gravitational force
- Electromagnetic force
- Strong nuclear force
- Weak nuclear force
- Normal force
- Elastic force
- Fictitious force
- The force imparted through a flexible medium (string, cable, chain, rope etc.) when a pulling force is applied to either one or both ends of that flexible medium.
- Tension force is a kind of contact force. Unlike rigid mediums like a rod of metal, for example, which can also be used to apply push force on an object, flexible mediums like rope and strings are not efficient at delivering the tension force to push an object. This is because if the force is applied towards the direction of the load meant to be moved, the flexible medium will go slack. After all, there is no tension in the rope anymore.
- In classical mechanics, a massless flexible medium can completely deliver the pulling force applied on one end without any loss in magnitude to the load connected at the other end. In this case, the flexible medium experiences two equal and opposite forces. One is the applied pulling force, and the other is a resistive force trying to restore the flexible medium to its original dimensions, which is called the tension force.
- Tension force can only act in a direction parallel to the length of the flexible medium. Tension force allows force to be transmitted over relatively large distances, with no to negligible loss in magnitude, and also enables to change the direction in which the force is applied.
The value of tension force can be given by T = mg + ma where
- T stands for the tension, the unit for which is N (newton)
- m indicates mass. The unit of mass is Kg (kilogram)
- g is for the gravitational force, which always has a constant value of 9.8 m/s
- a is the acceleration experienced by the body. The unit m/s
Examples of Tension Force
Real-life examples where tension force is an active component and can be observed is discussed below.
- Towing a car: When a car has unfortunately broken down in the middle of a busy highway, a tow truck is called for. The tow truck has a hook connected to a length of strong steel cable. This hook is attached to the broken-down car, and the truck is driven. The force produced by the truck is transferred through the cable and pulls the car along.
- Jumping rope: When a person skips using a jump rope, the rotational force produced by both their arms acts on the rope and maintains tension throughout the motion of the jump. If the force required to keep the rope spinning around the person is reduced, the jump rope goes slack.
- Bow: A genius example where the concept of friction was applied in earlier days is the composite bow, used for hunting and warfare. A composite bow consists of two important parts: a sturdy but flexible body (made from wood) and a string tied through the two ends of the piece of wood, forming a D-shape. When an arrow is to be knocked, it is pulled by the user, by which the tension in the body is transferred to the string. When it is let go, the tension force accelerates the arrow, making it fly.
- Trampoline: A trampoline consists of a flexible sheet stretched out over a metal body. When a person jumps on it, their weight acts as the load and pushes the sheet in. A resistive force (tension force) tries to pull the sheet back to its original position, making the person jump even higher.