The three main parts of an atom are protons, neutrons<span>, and </span>electrons<span>. </span>Protons<span> - have a positive charge, located in the </span>nucleus<span>, </span>Protons<span> and </span>neutrons<span> have nearly the same mass while </span>electrons<span> are much less massive. </span>Neutrons<span>- Have a negative charge, located in the </span><span>nucleus</span>
The time after being ejected is the boulder moving at a speed 20.7 m/s upward is 2.0204 s.
<h3>What is the time after being ejected is the boulder moving at a speed 20.7 m/s upward?</h3>
The motion of the boulder is a uniformly accelerated motion, with constant acceleration
a = g = -9.8 
downward (acceleration due to gravity).
By using Suvat equation:
v = u + at
where: v is the velocity at time t
u = 40.0 m/s is the initial velocity
a = g = -9.8
is the acceleration
To find the time t at which the velocity is v = 20.7 m/s
Therefore,

The time after being ejected is the boulder moving at a speed 20.7 m/s upward is 2.0204 s.
The complete question is:
A large boulder is ejected vertically upward from a volcano with an initial speed of 40.0 m/s. Ignore air resistance. At what time after being ejected is the boulder moving at 20.7 m/s upward?
To learn more about uniformly accelerated motion refer to:
brainly.com/question/14669575
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My answer is "Watt per square meter".
Answer:
I DONT KNOW WHAT TO DO SORRY
Explanation:
EVEN ME IM NOT SURW