Why can’t I see the video to see the answer I think those might be a glitch
Answer:
Explanation:
Given
coefficient of kinetic friction
=0.34
inclination 
weight of block=51 N
(a) When block is moving upward friction force acts downward
thus
as block is moving with constant velocity thus 
is zero
(b)When Block slides down the wall friction changes its direction to oppose the block
Answer:
The period of the wave does not change looting the value that accompanies the time, the wavelength does not change since it is the constant that accompanies x.
We see that the amplitude is twice the amplitude of the incident waves. Since the wave is stationary the velocity is zero
Explanation:
In this exercise we are given the equation of two traveling waves, it is asked to find the resulting wave
u = f + g
u = 2 sin (x + t) + 2 sin (x-t)
we will develop double angled breasts
u = 2 [(sin x cos t + sin t cos x) + (sin x cos t - sin t cos x)]
u = 2 [2 sin x cos t]
u = 4 sin x cos t
The period of the wave does not change looting the value that accompanies the time, the wavelength does not change since it is the constant that accompanies x.
We see that the amplitude is twice the amplitude of the incident waves. Since the wave is stationary the velocity is zero
The last one, the soil will become weak & unable to support plant growth
