To put an object into motion a force is usually required. No object can move in the absence of force. A force that is able to move an object without coming in direct contact with it is called an indirect force. It is also known as a non-contact force, distance force, or an invisible force.
Examples of Indirect Forces
1. Gravitational Force
Every object exerts a force of attraction on its neighboring object. The magnitude of this force is equal to the product of masses of both the objects divided by the square of the distance between them. This force of attraction is applied to every object present in nature. It is the natural pull of the earth that tends to hold the objects in position. When an object is thrown in the air it quickly falls back to the Earth’s surface. This is because the gravitational pull of the earth attracts the object towards it. The same force is responsible to keep the moon directed towards the earth.
2. Magnetic Force
When a magnet is brought near an iron nail, the nail gets attracted to it. The nail tends to move towards the magnet, sticks to it, and holds the position until both the objects are separated forcefully. An invisible force, called the magnetic force, acts on the nail and drags it towards the magnet. Hence, the magnetic force is a perfect example of indirect force.
3. Nuclear Force
The nuclear force is a force that is responsible to maintain the stability of an atom. These are of two types, namely strong interaction force and weak interaction force. A strong nuclear interaction force is the force of attraction that is accountable to bind the protons and neutrons together in the nucleus of an atom, while a weak interaction force results in the decay of the unstable nuclei. The nuclear force plays a very important role in the generation of nuclear energy by undergoing the process of nuclear fission and nuclear fusion. It is the strongest force in nature. It does not follow the inverse square law of distance.
4. Electrostatic Force
A force of interaction that exists between two charged bodies is called an electrostatic force. The electrostatic force is also known as static electricity. When an object is rubbed against some other object, the loosely bound electrons get transferred and the object gives up its state of equilibrium. This causes the body to develop a certain charge on it. This charge exerts a force of attraction or repulsion on a neutral or differently charged body. The electrostatic force is responsible for the sudden shock we feel after touching a metallic doorknob.
The forces in which an object exerts a force on another object by coming in contact with it are called direct forces. They are also known as contact forces. The direct force acts on the point of contact of the two objects.
Examples of Direct Forces
1. Push/Pull
Push or pull forces are the most commonly used forces to put an object in motion. Push force is the force that helps the object to move away from the person who is applying the force. Similarly, a pull force causes the object to move towards the person who is exerting the force. Since the person has to be in contact with the objects on which the force is being exerted, these forces are the best demonstration of contact forces.
2. Tension
Tension is a force that gets developed in a properly stretched rope. When a rope is pulled from both ends, it gets taut and a significant amount of tension force gets built in it. When the same rope is pushed, the rope gets loose and the tension gets lost. This tension force is used in a number of daily life applications such as a resistance band, a lat pulldown machine, etc. It is the opposite of the compression force.
3. Friction
Friction is the resistance to the motion. The best example of the existence of friction can be seen while rolling a ball on the floor. The force applied on the ball that causes it to move is opposed by another force that tends to slow down the speed of the ball and eventually makes it stop. Scientists believe that the force of friction exists as a result of the electromagnetic attraction between charged particles of two objects in contact.
4. Upthrust
The force exerted by the water molecules on the body that is completely or partially immersed into it is known as the upthrust force or the buoyant force. This force helps the light objects to float on the surface of the water. Upthrust force is also accountable to provide a justified reason for the fact that objects weigh less underwater. Greek scientist Archimedes was the first person to discover upthrust or buoyancy.