Calculating atomic mass, A practical approach

Dalton published his first table of relative atomic weights containing six elements (hydrogen, oxygen, nitrogen, carbon, sulfur and phosphorus), relative to the weight of an hydrogen atom. Since these were only relative weights, they do not have a unit of weight attached to them.

The basic approach for measuring mass of an hydrogen atom is discussed below. The amount of electricity passed through the electrolyte is directly proportional to the mass of any substance deposited or liberated at an electrode, according to Faraday’s law of electrolysis.

        m = Z q ;     m - mass,  q - charge,  Z - constant of proportionality

        

The constant 'Z' can be experimentally determined by taking ratio of hydrogen liberated at electrode and the charge transferred q = I × t . It is approximately equal to 96500 gm/C. 

So the amount of charge required for depositing one hydrogen atom is same as the charge of an H+ atom that is q = 1.6 × 10^-19. Thus the mass of one hydrogen atom liberated at an electrode should be simply Z times q.  

        Atomic mass =  96500  × 1.6 ×10^-19     = 1.6 ×10^-27 kg

        

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What is Centrifugal Force ?

Centrifugal is not a real force. It's just the equivalent of the force needed to be applied to overcome inertia as per Newton's second law. When a body is moving in a circular path with constant speed, its velocity is constant in magnitude but not in direction. Thus the rate of change of velocity is not zero. As the body keeps changing direction and has non-zero acceleration, there must be some force acting on it.

Let's assume a body of mass m moving on a circular path of radius r. The body moves by a small angle dθ in time dt. Distance traveled by the body during this time is given by the product of the radius of the circle and the angle subtended at the center that is rdθ. Therefore dt can be written as

The angle between two lines is the same as the angle between their perpendiculars. Therefore v1 and v2 are also having angle dθ between them. Taking the x-axis along v1 and the y-axis perpendicular to v1 and radially outwards

Change in velocity is difference of final and initial

Centrifugal force is oriented along the negative y-axis as per the assumed coordinate system which is the direction towards the center. So whenever the body is revolving in a circular motion with constant speed, a centripetal force towards the center is required to provide for the inertial force. Centrifugal is not one of the four fundamental forces or derived from them unlike centripetal force rather it is the result of newton's second law.

As a body in circular motion has acceleration towards the center, the person inside the body experiences a pseudo force in opposite direction i.e. radially outward. It is just like a person inside a lift moving upwards experiences a downward pull. This phenomenon leads to the common misconception that centrifugal force is something special force acting radially outward.

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