In a screw jack, the effort required to lift the load W is given by (where $$\alpha $$ = Helix angle and $$\varphi $$ = Angle of friction)

A. $${\text{P}} = {\text{W}}\tan \left( {\alpha - \varphi } \right)$$

B. $${\text{P}} = {\text{W}}\tan \left( {\alpha + \varphi } \right)$$

C. $${\text{P}} = {\text{W}}\tan \left( {\varphi - \alpha } \right)$$

D. $${\text{P}} = {\text{W}}\cos \left( {\alpha + \varphi } \right)$$

Answer: Option B