Answer:
ΔT = 59.9 ° C
Explanation:
For this exercise the brake energy is totally converted into heat
Let's calculate the vehicle energy
K = ½ m v²
Let's reduce the units to the SI system
v = 30 mph (1609.34 m / mile) (1h / 3600s) = 13.41 m / s
Em = K = ½ 1200 13.41²
K = 1.079 105 J
All this energy is transformed into heat
Em = Q
The expression for heat is
Q = m ΔT
ΔT = Q / m
The specific heat of iron is = 450 J / Kg ºC
ΔT = 1,079 105 / (4.0 450)
ΔT = 59.9 ° C
The speed of light in that medium is .
<u>Explanation:</u>
It is known that the light's speed is constant when it travels in vacuum and the value is . When the light enters another medium other than vacuum, its speed get decreased as the light gets refracted by an angle.
The amount of refraction can be determined by the index of refraction or refractive index of the medium. The refraction index is measured as the ratios of speed of light in vacuum to that in the medium. It is represented as η =
So, here η is the index of refraction of a medium which is given as 1.4, c is the light's speed in vacuum () and v is the light's speed in that medium which we need to find.
Thus the speed of light in that medium is