The spring force = kx = mg.
k is spring constant = 200 N/m
x is the spring elongation = 0.2 m
F = 200×0.2= 40 N
Now, F = mg wil be the weight of the object
Thus, weight is 40 N.
Thus, now we can also find the mass of object, m = F/g = 40 N/9.8
Because g is acceleration due to gravity = 9.8 m/sec ^2
m = 4.08 kg
When light moves from a medium with higher refractive index to a medium with lower refractive index, the critical angle is the angle above which there is no refracted ray, and it is given by:

(2)
where

is the refractive index of the second medium and

is the refractive index of the first medium.
We can find the ratio

by using Snell's law:

(1)
where

is the angle of incidence

is the angle of refraction
By using the data of the problem and re-arranging (1), we find

and if we use eq.(2) we can now find the value of the critical angle:
The element of a valid contract which is established by getting the signatures of all parties is <u>mutual agreement</u>
<h3>What is an element of a valid contract?</h3>
An element of a valid contract simply refers to that promise made between two or more parties that which allow the courts to make judgement.
Some elements of valid contract are:
- Offer
- Acceptance
- Consideration
- Intention to create legal relation
- Certainty and capacity.
So therefore, the element of a valid contract which is established by getting the signatures of all parties is mutual agreement
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