Answer:
25%
Explanation:
Efficiency is the ratio of power out to power in.
e = 20 W / 80 W
e = 0.25
The motor is 25% efficient.
The height need to change by 4 to double the final velocity.
<h3>Final velocity of the object</h3>
The final velocity of an object during a free fall is related to maximum height of fall as given the equation below.
v = √2gh
v² = 2gh
v²/h = 2g
v₁²/h₁ = v₂²/h₂
when v₂ = 2v₁, change in height is calculated as;
h₂ = h₁v₂²/v₁²
h₂ = (h₁ (2v₁)²) / (v₁)²
h₂ = 4h₁v₁² / v₁²
h₂ = 4h₁
Thus, the height need to change by 4 to double the final velocity.
Learn more about final velocity here: brainly.com/question/25905661
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The electrostatic force between the two ions is 
Explanation:
The electrostatic force between two charged particle is given by Coulomb's law:
where
is the Coulomb's constant
are the two charges
r is the separation between the two charges
In this problem, the ion of sodium has a charge of
while the ion of chlorine has a charge of
And the distance between the two ions is
Substituting, we find the electrostatic force between the two ions:
where the negative sign simply means that the force is attractive, since the two ions have opposite charge.
Learn more about electrostatic force:
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brainly.com/question/4273177
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I'm going to assume this is over a horizontal distance. You know from Newton's Laws that F=ma --> a = F/m. You also know from your equations of linear motion that v^2=v0^2+2ad. Combining these two equations gives you v^2=v0^2+2(F/m)d. We can plug in the given values to get v^2=0^2+2(20/3)0.25. Solving for v we get v=1.82 m/s!
