Answer:
d. All the above choices are correct.
Explanation:
When a spring of spring constant k is compressed by distance x , the potential energy stored in it is equal to
E = 1/2 k x²
If spring constant is 2 k , potential energy stored
E = 1/2 2k x²
= k x²
which is twice the earlier potential energy.
In the first case , the energy of spring is imparted to box . The energy given to box is spent by frictional force due to which box comes to rest.
So energy of box acquired from spring = work done by frictional force.
So energy of box acquired from spring = F X d , F is frictional force , d is displacement .
In the second case ,
energy acquired by box becomes two times
Work done by frictional force will also become two times to put box at rest
So displacement will be two times ( because frictional force is constant )
so option a is correct .
option b is also correct .
Because kinetic energy of box will be twice as explained above .
So option d will be correct.
