A smooth block is released from rest on a 4$5^o$ inclined plane and it slides a distance ‘d’. The time taken to slide is n times that on a smooth inclined plane. The coefficient of friction

• A

  ${\mathrm{\mu }}_{\mathrm{k}}=1-\frac{1}{{\mathrm{n}}^2}$

• B

  ${\mathrm{\mu }}_{\mathrm{k}}=\sqrt{1-\frac{1}{{\mathrm{n}}^2}}$

• C

  ${\mathrm{\mu }}_{\mathrm{k}}=\frac{1}{1-{\mathrm{n}}^2}$

• D

  ${\mathrm{\mu }}_{\mathrm{k}}=\sqrt{\frac{1}{1-{\mathrm{n}}^2}}$