Answer:
B) The tree was stationary and began to move.
Explanation:
This situation can be explained by using Newton's first law of motion, which states that
"An object at rest (or in motion at constant velocity) stays at rest (or in motion at constant velocity) unless a net non-zero force is exerted on it"
This means that an object at rest can start moving if and only if there is a net non-zero force acting on it.
In the example in the problem, the tree is initially stationary. Later, it started to move. According to Newton's first law, therefore, there must be a net force that caused this change of state of motion of the tree. Therefore, the correct answer is
B) The tree was stationary and began to move.
So to solve this problem, we must convert units and then cancel units simultaneously:
Therefore we know that the distance that light travels in one year is 
inches.
B. Both of these types of lenses have the ability to produce real images.
Answer:
t = 1.10 h
Explanation:
For this exercise we must calculate the intensity that reaches the cell with the polarizers, for this we use Malus's law
I = I₀ cos² θ
Let's calculate
I = I₀ cos² 60
I = I₀ 0.907
This is the intensity that reaches the cell
To find time, use an inverse proportion rule or rule of three, the intensity Io in
t = I₀ / (0.907 I₀) 1 h
t = 1.10 h
Answer: The magnitude of the force exerted on the roof is 490522.5 N.
Explanation:
The given data is as follows.
Below the roof, 
= 0 m/s
At top of the roof, 
= 39 m/s
We assume that 
is the pressure at lower surface of the roof and 
be the pressure at upper surface of the roof.
Now, according to Bernoulli's theorem,
= ![0.5 \times 1.29 \times [(39)^{2} - (0)^{2}]](https://tex.z-dn.net/?f=0.5%20%5Ctimes%201.29%20%5Ctimes%20%5B%2839%29%5E%7B2%7D%20-%20%280%29%5E%7B2%7D%5D)
= 
= 981.045 Pa
Formula for net upward force of air exerted on the roof is as follows.
F = 
= 
= 490522.5 N
Therefore, we can conclude that the magnitude of the force exerted on the roof is 490522.5 N.
