Answer:
a. Light pollution refers to light used for human activities that brightens the sky and hinders astronomical observations.
Explanation:
Light pollution is due to the excessive and misdirected use of artificial light. Light bulbs are often design in an incorrect way, since a great part of its light is not completely directed to the ground and an important percentage is emitted to the sky in where will be scattered and reflected back to ground by the particles in the atmosphere. That brings as an effect a sky glow, therefore the visibility of astronomical objects will be extremely reduce.
Hence, professional astronomical research and amateur observations will be affected. Light pollution has a negative impact on bird migration at night and in the health of difference species, humans also.
Answer: Last option
2.27 m/s2
Explanation:
As the runner is running at a constant speed then the only acceleration present in the movement is the centripetal acceleration.
If we call a_c to the centripetal acceleration then, by definition

in this case we know the speed of the runner

The radius "r" will be the distance from the runner to the center of the track



The answer is the last option
Answer:
Vf = 10.76 m/s
Explanation:
Train kinematics
The train moves with uniformly accelerated movement
Formula (1)
Vf: Final speed (m/s)
V₀: Inital speed (m/s)
t: time in seconds (s)
a: acceleration (m/s²)
Movement from t = 0 to t = 5.2s
We replace in formula (1)
4.6 = 0 + a*5.2
a = 4.6/5.2 = 0.88 m/s²
Movement from t = 5.2s to t = 5.2s + 7s = 12.2s
We replace in formula (1)

Vf = 10.76 m/s
Answer:
127.4 newtons
Explanation:
Assuming g = 9.8:
F = ma = 13(9.8) = 127.4 N