Answer:
When you release the opening of the balloon, gas quickly escapes to equalize the pressure inside with the air pressure outside of the balloon. The escaping air exerts a force on the balloon itself. ... That opposing force—called thrust, in this case—propels the rocket forward.
The magnetic field strength in a coil is directly proportional to the number of turns, or loops, in the coil.
Therefore, when there are four loops instead of one, the magnetic field strength has increased four times, making it harder to push the magnet in.
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:
brainly.com/question/8960054
brainly.com/question/4273177
#LearnwithBrainly
The choices are confusing. Air, oil, and alcohol are fluids at any reasonable temperature. Dry cement is not.
Answer:
d = 0.05 [m] = 50 [mm]
Explanation:
We must remember the principle of conservation of energy which tells us that energy is transformed from one way to another. For this case, the initial kinetic energy is transformed into useful work that is equal to the product of force by distance.
![E_{k}=F*d\\400 = 8000*d\\d = 0.05 [m] = 50 [mm]](https://tex.z-dn.net/?f=E_%7Bk%7D%3DF%2Ad%5C%5C400%20%3D%208000%2Ad%5C%5Cd%20%3D%200.05%20%5Bm%5D%20%3D%2050%20%5Bmm%5D)