Initially spring is in its natural length. Now block of mass $0.25 \mathrm{~kg}$ is released, then find out maximum force by system on the floor.

• A

  $15 \mathrm{~N}$
• B

  $20 \mathrm{~N}$
• Correct answer
  C

  $25 \mathrm{~N}$
• D

  $30 \mathrm{~N}$

Solution

By using work - energy theory on $(0.25) \mathrm{kg}$ $\begin{aligned} & \frac{1}{2} k x^2=m g x, \text { where } m=2 \mathrm{~kg} \\ & k x=2 m g=2 \times 0.25 \times 10=5 \mathrm{~N} \\ & N=k x+2 \times 10=5+20=25 \mathrm{~N}\end{aligned}$

Hence, the correct answer is option: 'C'.