Answer:
The vibrational frequency of the rope is 5 Hz.
Explanation:
Given;
number of complete oscillation of the rope, n = 20
time taken to make the oscillations, t = 4.00 s
The vibrational frequency of the rope is calculated as follows;

Therefore, the vibrational frequency of the rope is 5 Hz.
A. Solid
Solid structures are actually made of repeating patterns.
Effort force and Resistance force
Its called static friction.
No, energy transformation is occurring in every point of the motion.
In fact, the ball starts from point 1 with maximum kinetic energy and zero potential energy (taking the hand of the boy as reference level). The kinetic energy converts into gravitational potential energy as it goes higher: in point 2, part of the kinetic energy has converted into potential energy (because the velocity has decreased, while the height has increased), and then when the ball reaches point 3 all the kinetic energy has converted into potential energy (because now the velocity is zero, while the height is maximum). As the ball descends (point 4), the velocity starts to increase again, therefore the kinetic energy increases and the potential energy decreases (because the height is deacreasing now).
Summarizing, energy transformation is occuring in every point of the motion.