B celcius to kelvin, I know this answer :) i wont troll
Answer:

Explanation:
The speed of light through a medium is given by:

where
is the speed of light through vacuum
n is the index of refraction of the material
In this case, diamond has a refractive index of n = 2.4, so the speed of light in diamond is

Weight of object = mass x acceleration due to gravity
= 2.5 x 9.8
= 24.5N
Hence option B is correct.
Hope this helps!!
Answer: 15.6 metres
Explanation:
Given that:
length of wave (λ)= ?
Frequency of wave F = 28 Hertz
Speed of wave (V) = 437 m/s
The wavelength is the distance covered by the wave in one complete cycle. It is measured in metres, and represented by the symbol λ.
So, apply V = F λ
Make λ the subject formula
λ = V / F
λ = 437 m/s / 28 Hertz
λ = 15.6 m
Thus, the length of the wave is 15.6 metres
The question isn't clear enough, I think it ask us to calculate the linear speed of a point at the edge of the DVD.
Now let's imagine we're a point at the edge of the DVD, we're undergoing a circular motion. Each minute we will complete a circular track 7200 times, now we need to know the distance we travel each turn. The perimeter of the DVD, a circular object is:

Know recall that:

We now need to know how much distance is traveled during a minute or 60 seconds:

Finally we divide this result with t=60 seconds:


Where the distance units were named units as the length unit is not specified in this exercise.<span />