Answer:

Work done to bring three electrons from a great distance apart to 3.0×10−10 m from one another (at the corners of an equilateral triangle) is 
Explanation:
The potential energy is given by:
U=Q*V
where:
Q is the charge
V is the potential difference
Potential Difference=V=
So,

Where:
k is Coulomb Constant=
q is the charge on electron=
r is the distance=
For 3 Electrons Potential Energy or work Done is:


Work done to bring three electrons from a great distance apart to 3.0×10−10 m from one another (at the corners of an equilateral triangle) is 
Speed= distance/time
Speed= 150000m/7200s=20.83m/s(cor.to.2d.p.)
Answer:
Momentum is conserved.
Explanation:
-Momentum is conserved.
-By Newton's third law (For every action, there is an equal and opposite reaction.)-the change in momentum of gases in one direction must be balanced by an equal change in momentum of the spacecraft in the opposite direction.
When the magnets are released and begin to move, the magnetic force changes potential energy into kinetic energy;<u> option D</u>
<h3>What is magnetic force?</h3>
Magnetic force can be defined as the force of attraction or repulsion that is felt or produced between the magnetic poles and electrically charged moving particles.
Magnetic force is the force that exists due to the attractio or repulsion of objects place around the region of space where a maget exerts its force.
When a magnet is released ai a system of magnets and allowed to move it increases the kinetic eergy of the system by converting potential energy to kinetic energy.
Learn more about magnetic force at: brainly.com/question/28989998
#SPJ1