Answer:
A planetesimal is an object formed from dust, rock, and other materials. The word has its roots in the concept infinitesimal, which indicates an object too small to see or measure. Planetesimals can be anywhere in size from several meters to hundreds of kilometers.
Protoplanets are thought to form out of kilometer-sized planetesimals that gravitationally perturb each other's orbits and collide, gradually coalescing into the dominant planets.
Answer:
o The result of a chemical change is a different composition; in a physical change, the composition remains the same.
Explanation:
In a chemical change, new kinds of matter are produced although the atoms are the same.
For physical changes, no new kinds of matter formed. Only the state of substances changes.
- Most chemical changes are usually irreversible
- Physical changes are reversible in most parts.
- Changes in state and form are salient characteristics of physical changes.
- When new products are formed from the reactants, it is an indicator of a chemical change.
Answer:
t=4.86s
Explanation:
To find the wavelength you use the following formula:
v: speed of sound = 343m/s
f: frequency = 400Hz
λ: wavelength of the sound
By doing λ the subject of the formula and replacing the values of f and v you obtain:
Now, to calculate the time that sound takes to reach the last row you use:
t: time
d: distance to the last row = 1947m
hence, the time is 4.86s
Answer: 
Explanation:
We can solve this with the Law of Universal Gravitation and knowing the acceleration due gravity 
of an object above the surface of the planet decreases with the distance (height) of this object from the center of the planet.
Well, according to the law of universal gravitation:
(1)
Where:
is the module of the force exerted between both bodies
is the gravitational constant
is the mass of the Earth
are the mass of each communications satellite
is the distance between the center of the Earth and the satellite
is the radius of the Earth
is the height of the satellite, measured from the Earth's surface
On the other hand, we know according to <u>Newton's 2nd law of motion:</u>
(2)
Combining (1) and (2):
(3)
Isolating :
(4)
Remembering :
(5)
Finally:
Construction, like building a home/building, digging, like in a mine, and opening a soda can, where the part to open is a lever.
