Answer:
The answer is indeed E, 4K1.
Step-by-step explanation:
When the block is compressed a distance x from equilibrium, the spring exerts a restoring force on the block given by Hooke's law:
F = -kx
where k is the spring constant. The negative sign indicates that the force is in the opposite direction to the displacement.
As the block is released, this restoring force accelerates the block to the right. At any point during the motion, the total mechanical energy (kinetic plus potential) of the system is conserved. Initially, all the energy is potential energy stored in the compressed spring. At the point when the block separates from the spring, all the potential energy has been converted into kinetic energy. Therefore, we have:
K = (1/2)mv1^2 = (1/2)kx^2
where v1 is the speed of the block when it separates from the spring.
When the block is compressed a distance 2x, the spring exerts a restoring force given by:
F = -2kx
This force is twice as large as the force when the block was compressed a distance x. Therefore, the block will experience twice the acceleration and reach twice the speed when it separates from the spring. The kinetic energy of the block at this point is given by:
K' = (1/2)mv2^2 = (1/2)k(2x)^2 = 4kx^2
where v2 is the speed of the block when it separates from the spring after being compressed a distance 2x.
So the ratio of the kinetic energies when the block is released from compressions of distance x and 2x respectively is:
K'/K = 4kx^2 / (1/2)kx^2 = 8
Therefore, the kinetic energy of the block when it separates from the spring after being compressed a distance 2x is 8 times the kinetic energy when it is compressed a distance x, i.e., K' = 8K. So the answer is E, 4K1