Your Question:
<span>A
star is born when gas and dust from a nebula become so dense and hot
that nuclear fusion starts. Which of the following forces is responsible
for the formation of a star?
A.
friction
B.
gravitation
C.
magnetism
D.
electromagnetic energy</span>
Our Teams Answer: B. Gravitation
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-ExperimentsDIY
The total momentum is unchanged according to the law of conservation of momentum. When the gun is fired, the bullet gains a high velocity forward (positive velocity), and that velocity multiplied by its mass is the momentum the bullet gains. Therefore, the gun must gain a momentum backwards to cancel out that momentum forward, so the gun recoils back with a negative velocity.
We use the equation of motion for vertical component,
Here, 
is displacement of bullet, 
is vertical initial velocity of bullet which is equal to zero because bullet was fired horizontally, and t is time of flight.
Therefore,
Given, 
Substituting the values, we get time of flight
