Answer:
The fraction of kinetic energy to the total energy is 
.
Explanation:
displacement is one third of the amplitude.
Let the amplitude is A.
x= A/3
The kinetic energy of the body executing SHM is
The total energy is
Divide (1) by (2)
Find the amount of work that the spring does. This can be found using the equation 1/2kx^2. Then, you must set that equal to the amount of kinetic energy the car has. This is possible thanks to the work-energy theorem.
1/2kx^2 = 1/2mv^2
Solve to find velocity. Remember, the spring is displaced .15 m, not 15!
To find the acceleration, use F = ma. The force being applied to the car is kx, and you know the mass. You do the math.
For problem C I don't know, haven't done that yet in my class. Sorry!
It must be the same force, because when it is applied, it is 'distributed' equally in each of the points (either a tendon or a wire or a rope or something similar). The 128N resistance should be preserved for tendons that have the same diameter.
Therefore the correct answer is A.
