<h2>Answer: Gravitational attraction
</h2>
Gravity force causes the clouds of dust and gas to form a protostar. As this <u>attraction force</u> is responsible for gathering and compressing the existing elements in the cloud of gas and dust, heating them during this process.
Then, when the amount of material accumulated by gravitational contraction is large enough, and the temperature and pressure reached high enough, the <u>nuclear fusion</u> process will begin.
To understand it better: The hydrogen nuclei will begin to fuse, generating helium nuclei in the process and releasing huge amounts of energy.
It should be noted that the protostars radiate half of the energy contributed by the gravitational collapse and the other half is invested in heating its core.
<em>Answer:</em>
<em>Velocity is vector quantity.So it needs direction in addition to speed.</em>
<em>Explanation:</em>
<em>The velocity of an object is the rate of change of its position with respect to a frame of reference, and is a function of time. Velocity is equivalent to a specification of its speed and direction of motion. </em>
Answer:
539 kPa
Explanation:
Pressure equals density times acceleration of gravity times depth.
P = ρgh
Water has a density of 1000 kg/m³, and acceleration of gravity is 9.8 m/s².
P = (1000 kg/m³) (9.8 m/s²) (55.0 m)
P = 539,000 Pa
P = 539 kPa
Let's calculate the average acceleration. It is the rate of changing speeds. Hence, we need to calculate the difference of speeds. 10-6=4 m/s. The rate is now

.
In general, the formula for the mean acceleration between two times 1 and 2 is given by:

where v1 and v2 are the speeds at the respective points and T is the time interval between them.
Answer:
8 m west
Explanation:
If we say east is the +x direction, and west is the -x direction, then the displacement is:
Δx = 12 m + (-20 m)
Δx = -8 m