Solution :
From the given data,
For the spherical shell is 
where x is the radius of gyration and the acceleration of a rolling body on an inclined plane = a
Therefore,
= 0.6 x 9.81 x sin ( 29.7)
Δt = 1.411 s
Weight = (mass) x (gravity)
Weight = (8 x 10⁻⁴ kg) x (10 N/kg) = 0.008 Newton
Refraction is the change in direction of a wave, caused by the change in the wave's speed. Examples of waves include sound waves and light waves. Refraction is seen most often when a wave passes from one transparent medium to another transparent medium. Different types of medium include air and water. When a wave passes from one transparent medium to another transparent medium, the wave will change its speed and its direction. For example, when a light wave travels through air and then passes into water, the wave will slow and change direction.
The answer is c .Frequency
4 fundamental forses are: strong, electro-magnetic, weak, gravity.
The strong force is the force which can hold nucleus together against enormous forces of repulsion of the protons is strong indeed. In comparasing to electro magnetic force, this force in not an inverse square and it has very short range.
The electro-magnetic force manifests itself as trough the forces between charges(Colubos law) and the magnetic force, both of which are summarized in the Lorentz force law. The electro-magnetic force holds atoms and moleculs together.
The weak force is a force between elementary particles certain processes that take place with low probability, as radio-active beta-decay and collisions between neutrinos and other particles.
The gravity force is the weakest of all 4 fundamental forces. It is the force of attraction between all masses in the universe, especially the attraction of the earth's mass for bodies near its suface. Newton's law of gravity states that gravitational force between two bodies is proportional to the product of their masses and inversely proportional to the square of the distance between them.
