Answer:
Explanation:
Tides occur mainly in oceans because that is basically one huge body of water that is free to move all over the earth. Lakes and rivers do not cover enough area to have their water be moved significantly by gravity, or in other words, to have tides.
Answer: C
Explanation:
In collision, whether elastic or inelastic collisions, momentum is always conserved. That is, the momentum before collision will be equal to the momentum after collision.
Change in momentum of the system will be momentum after collision minus total momentum before collision.
Since momentum is a vector quantity, the direction will also be considered.
Momentum = MV - mU
Let
M = 800 kg is going north
at V = 20 m/s and the other car
m= 800 kg is going south
at U = 10m/s.
Substitute all the parameters into the formula
Momentum = (800 × 20) - (800 × 10)
= 8000 kgm/s
The final momentum after collision will also be equal to 8000 kgm/s
Change in momentum = 8000 - 8000
Change in momentum = 0
Answer:
a) 
b) infrared region
Explanation:
Photon energy is the "energy carried by a single photon. This amount of energy is directly proportional to the photon's electromagnetic frequency and is inversely proportional to the wavelength. If we have higher the photon's frequency then we have higher its energy. Equivalently, with longer the photon's wavelength, we have lower energy".
Part a
Is provide that the smallest amount of energy that is needed to dissociate a molecule of a material on this case 0.42eV. We know that the energy of the photon is equal to:

Where h is the Planck's Constant. By the other hand the know that
and if we solve for f we have:

If we replace the last equation into the E formula we got:

And if we solve for
we got:

Using the value of the constant
we have this:


Part b
If we see the figure attached, with the red arrow, the value for the wavelenght obtained from part a) is on the infrared region, since is in the order of 
6 months with no sunrise and the other 6 without a sunset, at some places on Earth, are the result of the orientation of Earth's axis.