Answer:
Part a)

Part b)

Part c)

Explanation:
As per Newton's II law we know that
F = ma
so we will have

so we will have

Part a)



Part b)



Part c)



Answer:
c. (H-h/2) above the ground
Explanation:
The mirror must be at least half as tall as the alien, and its base must be located at half of the distance between the alien's eyes and the ground (assuming that the alien doesn't float or levitate).
This question is about the Law of Reflection which states that the angle of reflection = angle of incidence.
I attached an image that can help you understand the concept, although the alien is not included.
Answer:
c. 2 m/s
Explanation:
The speed of a wave is given by:

where
v is the speed of the wave
f is the frequency
is the wavelength
For the wave in this problem, we have
f = 4 Hz is the frequency
is the wavelength
So, the speed of the wave is

Diffraction is observable when the is smaller than the wavelength
Answer:
F' = F
Explanation:
The gravitational force of attraction between two objects can be given by Newton's Gravitational Law as follows:

where,
F = Force of attraction
G = Universal gravitational costant
m₁ = mass of first object
m₂ = mass of second object
r = distance between objects
Now, if the masses and the distance between them is doubled:

<u>F' = F</u>