the light intensity of a source is 100 Candelas. The illuminance on a surface is 4 Lux. How far is the surface from the source
2 answers:
Answer:
The surface from the source is 5 m.
Explanation:
Given that,
Light intensity = 100 candelas
Illuminance = 4 lux
The formula of illumination is
According to illumination law,
The intensity of illuminance of the the light source is inversely proportional to the square of the distance from the source.
The formula of illumination is
Where, E = illuminance
I = luminous Intensity of the light
D = distance
We substitute the value into formula
Hence, The surface from the source is 5 m.
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Answer:
v₀ = 280.6 m / s
Explanation:
we have the shock between the bullet and the block that we can work with at the moment and another part where the assembly (bullet + block) compresses a spring, which we can work with mechanical energy,
We write the mechanical energy when the shock has passed the bodies
Em₀ = K = ½ (m + M) v²
We write the mechanical energy when the spring is in maximum compression
½ (m + M) v² = ½ k x²
Let's calculate the system speed
v = √ [k x² / (m + M)]
v = √[152 ×0.78² / (0.012 +0.109) ]
v = 27.65 m / s
This is the speed of the bullet + Block system
Now let's use the moment to solve the shock
Before the crash
p₀ = m v₀
After the crash
The system is formed by the bullet and block assembly, so the forces during the crash are internal and the moment is preserved
m v₀ = (m + M) v
v₀ = v (m + M) / m
let's calculate
v₀ = 27.83 (0.012 +0.109) /0.012
v₀ = 280.6 m / s