A is pulling the block straight down toward the center of the Earth, no matter what the slope of the plane may be. A is the force of gravity.
The directions of B and C both depend on the slope of the plane.
B is a force that's parallel to the plane, pulling the block UP the plane. B is the force of friction.
C is a force perpendicular to the plane, preventing the block from falling down through the plane. C is the normal force.
Answer: A- A truck has a mass of 900 kilograms.
If the velocity of the truck is 20 m/s, what is its momentum?
1- 180000 kg·m/s
2-0 kg·m/s
3-9000 kg·m/s
4-18000 kg·m/s
Answer:
t = 1.62 h
Explanation:
A flat mirror fulfills the law of reflection where the incident angle is equal to the reflected angle.
θ_i = θ_r
If we use trigonometry to find the angles, the mirror is at a height of L = 1.87 m, and the reflected rays reach a distance x1 = 3.56 m
tan θ₁ = x₁ / L
tan θ₁ = 
θ₁ = tan⁻¹ 1.90
θ₁ = 62.29º
for the second case x₂ = 1.46 m
tan θ₂ = x₂ / L
θ₂ = tan⁻¹ 
θ₂ = 37.98º
the difference in degree traveled is
Δθ = θ₁- θ₂
Δθ = 62.29 - 37.98
Δθ = 24.31º
as in the exercise they indicate that every 15º there is an hour
t = 24.31º (1h / 15º)
t = 1.62 h