Answer: Gravity has an effect of a gravitational pull, which keeps things on the ground instead of floating around like we are in space.
<h2>
Hello!</h2>
The answer is A. the principal energy level
<h2>Why?</h2>
The principal energy level or principal quantum number n, tell us about the position of an determined electron in the energy levels relative to the greater average distance of an electron from the nucleus, the larger the value of n and the higher its energy.
The principal energy levels contains n sublevels, 
orbitals and 
electrons.
For example, the number 1, has one orbital which is contained in a energy sublevel, its called s orbital, and it's just an orbital with 2 electrons.
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Their is going to be 4 sig figs
Given
Weight of the block A, Wa = 20 lb, weight of block B Wb = 50 lb. Applied
force to block A, P = 6lb, coefficient of static friction µs = 0.4, coefficient
of kinetic friction µk = 0.3. If a force P
is applied to the body, no relative motion will take place until the applied
force is equal to the force of friction Ff, which is acting opposite to the
direction of motion. Magnitude of static force of friction between block A and
block B, Fs = µsN, where N is
reaction force acting on block A. Now, resolve the forces Fx = max. P = (mA +
mB)a,
6 = (20 / 32.2 + 50 / 32.2)a
2.173a = 6
A = 2.76 ft/s^2
To check slipping occurs between block A and block B, consider block A:
P – Ff = mAaA
6 – Ff = 1.71
Ff = 4.29 lb
And also,
N = wA. We know static friction,
Fs = µsN
Fs = 0.4 x 20
Fs = 8lb
Frictional force is less than static friction. Ff < Fs
<span>Therefors, acceleration of block A, aA = 2.76 ft/s^2, acceleration of
block B aB = 2.76 ft/s^2</span>
When 2 waves interefere (or collide with eachother), it usually affects the crest of the wave. If both waves collide with both crests, it will create an amplified crest, and the waves will pass through eachother afterwards. If a trough of a wave meets a crest, it will cause the crest to be lowered shortly before both continue on.
