Force is a push or pull that changes an object’s motion. It has both size and direction and can make an object move, stop, or change direction. An example of a force is gravity.
Force is a basic concept in physics that describes an interaction between two objects that causes a change in the motion of one or both of the objects. In physics, forces are often used to explain why objects move the way they do. For example, if you push a book across a table, the force of your hand on the book is what causes it to move. Forces can also cause objects to change direction, speed up, slow down, or remain at rest. Forces can be classified into two main categories: contact forces and non-contact forces. Contact forces are forces that are transmitted through physical contact between two objects, while non-contact forces are forces that act at a distance, without physical contact.
Contact forces can be further classified into four types: friction, tension, normal force, and air resistance.
Friction:
Friction is a force that opposes motion between two objects that are in contact. Friction is generated by the microscopic roughness of the surfaces in contact. The force of friction depends on the type of surface and the force that is applied. The coefficient of friction is a measure of the strength of the frictional force.
Tension:
Tension is a force that is transmitted through a rope, cable, or string. Tension is the force that is required to keep the rope taut. The force of tension is equal to the force applied to one end of the rope, and it decreases as the rope is stretched.
Normal Force:
The normal force is a force that acts perpendicular to a surface and is exerted by the surface on an object that is in contact with it. The normal force is equal in magnitude to the weight of the object, but in the opposite direction. The normal force is essential in determining the stability of an object and the direction of motion.
Air Resistance:
Air resistance is a force that opposes motion through the air. The force of air resistance depends on the velocity of the object, the surface area, and the density of the air. Air resistance can be reduced by decreasing the surface area or by increasing the speed of the object.
Non-contact forces can be further classified into three types: gravitational force, electromagnetic force, and nuclear force.
Gravitational Force:
Gravitational force is a force that acts between two objects that have mass. The force of gravity depends on the masses of the objects and the distance between them. Gravitational force is the force that keeps the planets in orbit around the sun.
Electromagnetic Force:
Electromagnetic force is a force that acts between charged objects. The force of electromagnetic force depends on the charge and the distance between the objects. Electromagnetic force is responsible for the forces between charged particles, such as ions and electrons.
Nuclear Force:
Nuclear force is a force that acts between the nuclei of atoms. The force of nuclear force depends on the distance between the nuclei and the charge of the nuclei. Nuclear force is responsible for the stability of the nucleus and the binding of the protons and neutrons.
Solids have definite shapes and sizes; however, it is possible to change their shapes and sizes by applying external forces. When the external force is removed, the object tends to return to its original shape and size. This behaviour is called elastic behaviour. Solids can be stretched, squashed, bent or twisted.
Springs are often used to model elastic materials, which are able to return to their original shape after being deformed by an applied force. As springs are designed to stretch a long way when force is applied, therefore it is easy to measure changes in their lengths. Consider a spring hung from a rigid support, so that its top end is fixed. Weights are hung on the other end of the spring. These are called loads. As load is increased, the spring is stretched and its length increases. When the load is removed, the spring returns to its original length. This is called elastic change. The stretching of springs has many practical applications, such as in mechanical systems, suspension systems in vehicles, and in measuring instruments, such as spring scales. By understanding the behaviour of springs when they are stretched, we can design and engineer systems that make use of this relationship in a controlled and predictable manner.
The length of spring increases as the force (load) increases. This increase in length of spring is known as extension.
Hence;
Length of stretched spring = Original length + Extension
Elasticity is a property of materials that refers to their ability to return to their original shape after being deformed by an applied force. In physics, elasticity is a fundamental concept that is used to describe the behaviour of materials under stress and strain.
Imagine a rubber band, which can be stretched and pulled but will eventually return to its original shape when the force is removed. This is an example of elastic behaviour. The amount by which a material can be stretched or compressed before it breaks is known as its elastic limit.