It takes twice the force to produce the same acceleration in the 2kg rock.
As the surface given is a smooth surface, we can use specular reflection. According to the law of specular reflection, the angle of incidence equals the angle of reflection, so it will also be 40°. Answer is A.
Answer:
It will not change
Explanation:
The period of oscillation of a mass-spring system is given by

where
T is the period
m is the mass hanging on the spring
k is the spring constant
As we see from the formula, the period of oscillation does not depend on the amplitude of the motion: therefore, if we change the amplitude, the time for one oscillation will not change.