I think it’s the second one: magnetic domains must come in pairs—one north and one south
I believe it's technically referred to as the Normal force.
However I like to think of it as the reaction force, as it is the force that is a result of obeying Newton's 3rd law ("<span>For every action, there is an equal and opposite reaction"). The upward force from the ground is the reaction to the downward force of gravity.</span>
A) <u>Weight = mass × acceleration (due to gravity) </u>
= 60×9.8
= 588 N
<u>B) Potential energy = mass x gravity x change in height
</u>
1,000 = 60.0 x 9.8 x h
h = 1.7 m
<u>C) Kinetic energyF = potential energyI
</u>
KEF = 1/2mv2
PEI = mgh = 1,000 J
1/2mv2 = 1,000
1/2(60.0)v2 = 1,000
v2 = 33.33
v = 5.77 m/s
<span>Hooke's law is F=-kx, which means the elastic force contained by the spring is a product of the distance it stretches and its spring constant, but the direction of the force is opposite that of the displacement. We calculate as follows:
</span><span>(3 kg)(9.8 m/s^2) = -k(-0.38 m)
</span>k =<span> 77.4
</span><span>Then use k to find the new displacement, again using Hooke's law:
(7 kg)(9.8 m/s^2) = -(77.4)x
x = -0.89 m</span>