Answer:
4.42 x 10⁷ W/m²
Explanation:
A = energy absorbed = 500 J
η = efficiency = 0.90
E = Total energy
Total energy is given as
E = A/η
E = 500/0.90
E = 555.55 J
t = time = 4.00 s
Power of the beam is given as
P = E /t
P = 555.55/4.00
P = 138.88 Watt
d = diameter of the circular spot = 2.00 mm = 2 x 10⁻³ m
Area of the circular spot is given as
A = (0.25) πd²
A = (0.25) (3.14) (2 x 10⁻³)²
A = 3.14 x 10⁻⁶ m²
Intensity of the beam is given as
I = P /A
I = 138.88 / (3.14 x 10⁻⁶)
I = 4.42 x 10⁷ W/m²
Answer:
0.43
Explanation:
Sum of forces in the y direction:
∑F = ma
N − mg = 0
N = mg
There are friction forces in two directions: centripetal and tangential. The centripetal acceleration is:
ac = v² / r
ac = (35 m/s)² / 564 m
ac = 2.17 m/s²
The total acceleration is:
a = √(ac² + at²)
a = √((2.17 m/s²)² + (3.62 m/s²)²)
a = 4.22 m/s²
Sum of forces:
∑F = ma
Nμ = ma
mgμ = ma
μ = a / g
μ = 4.22 m/s² / 9.8 m/s²
μ = 0.43
Answer:
C, 4.5 billion years ago, i think
Explanation:
Power of a lens is measured by f/D ratio where f is the focal length and D is the diameter of the lens (or mirror). The ratio gives you the power of an optical device or the light gathering power. Please remember a lens focuses the light. Imagine it as a light funnel. A lens works similar to a funnel. It bends the light rays and bring them to a concentrated spot or the focus, just like a funnel that gathers a liquid and bring it out through a narrow spout. Bigger the diameter of the funnel more liquid it can handle. Same way larger diameter of the lens more light it can bring to focal point. That is how you get f/D ratio.
I hope this makes it somewhat clear?
It has to show all loops closed and all lights on to be a closed circuit
