**Definition **

A quantity competent enough to modify the size, shape, or motion of an object is termed as force. In other words “A force is an influence (such as a push, gravity, or friction) that causes an object either to change its velocity or to store energy through deformation”.1

Since force is a vector quantity, it has got both direction and magnitude. In case, a body is in motion, the energy of its motion can be quantified as the momentum of the object i.e. the product of its mass and its velocity. When the body is free to move, its velocity will be changed by the action of a force.

**Units of Measurement**

The precise measurement of force is significant in many areas, like engine thrust determination, the weighing of large structures, and materials testing. The magnitude of a force is measured in:

- Newtons (In the SI system): One Newton is defined as the force required to accelerate a mass of one kilogram at a rate of one meter per second, per second
- Pounds (In the British/American system)

**Basic Forces**

Four basic forces found in nature are:

**Gravitational Force:**It is the force of attraction between any two bodies in the universe. It is the weakest of all and also the easiest to observe. It is always attractive and has an infinite range.**Magnetic Force:**It can be the force between two magnets or force on a magnet placed in a magnetic field. It can be either attractive or repulsive.**Strong nuclear Force:**It is a strong force with a short range. It is a non-central force which acts within the nucleus. It is not directed along the line joining the centers of the interacting particles.**Weak nuclear Force:**Its range is shorter than the strong nuclear force and this type of force is considered only for certain nuclear processes like radioactive beta decay.

**Pressure**

It is the ratio between force acting on a surface and the area of that surface. It is measured in units of force divided by area:

- Pounds per square inch (psi)
- Newtons per square meter, or Pascals

Whenever an object is subjected to an external stress i.e. pressure with the aim to cause a reduction in its volume, this process is called compression. The majority of liquids and solids are practically incompressible, whereas gases are not.

**Boyle’s Law**

It is the first Gas Law which states that the pressure and volume of a gas are inversely proportional to one another i.e. PV = k, where P is pressure, V is volume and k is a constant of proportionality.

**Charles’ Law**

It is the Second Gas Law which states that the volume of an enclosed gas is directly proportional to its temperature i.e. V = kT, where T is its absolute temperature.

**Third Gas Law**

According to this law, the pressure of a gas is directly proportional to its absolute temperature i.e. P = kT. After combining the three relationships we get the ideal gas law i.e. PV = kT. This approximate relationship holds accurate for many gases at relatively low pressures and high temperatures.

**References**

- NPL

I want effects of force