To solve this problem we will apply the concepts related to the balance of forces. We will decompose the forces in the vertical and horizontal sense, and at the same time, we will perform summation of torques to eliminate some variables and obtain a system of equations that allow us to obtain the angle.
The forces in the vertical direction would be,



The forces in the horizontal direction would be,



The sum of Torques at equilibrium,




The maximum friction force would be equivalent to the coefficient of friction by the person, but at the same time to the expression previously found, therefore


Replacing,


Therefore the minimum angle that the person can reach is 46.9°
Answer: The sound will change due to changes in frequency and the wavelength of the airplane.
Explanation: Let assume that the observer is at a stationary position. The wavelength of the sound from the airplane reduces and the frequency increases as the plane is moving toward the observer. As the airplane passes by, that is, moving away from the observer, the frequency starts to reduce while the wavelength of the sound starts to increase.
The sound that the observer hears will change base on the illustration above.
The formula we can use in this case is:
d = v0t + 0.5 at^2
v = at + v0
where,
d = distance travelled
v0 = initial velocity = 0 since at rest
t = time travelled
a = acceleration
v = final velocity when it took off
a. d = 0 + 0.5 * 3 * 30^2
d = 1350 m
b. v = 3 * 30 + 0
<span>v = 90 m/s</span>
There is kinetic energy when it is sitting at the top, then as it goes towards the bottom, the kinetic energy is transformed into potential energy.