A block placed on a horizontal surface is being pushed by a force F making an angle $\mathrm{\theta }$ with the vertical. The coefficient of friction between block and surface is $\mathrm{\mu }$. The force required to slide the block with uniform velocity on the floor is:

• A

  $\frac{\mathrm{\mu mg}}{(\sin \mathrm{\theta }-\mathrm{\mu } \cos \mathrm{\theta })}$

• B

  $\frac{(\sin \mathrm{\theta } - \mathrm{\mu } \cos \mathrm{\theta })}{\mathrm{\mu mg}}$

• C

  $\mathrm{\mu mg}$

• D

  none of these