question_answer

A block of mass 50 kg can slide on a rough horizontal surface. The coefficient of friction between the block and the surface is 0.6. The least force of pull acting at an angle of 30° to the upward drawn vertical which causes the block to just slide is                           [ISM Dhanbad 1994]

A)                         29.43 N                      

B)                         219.6 N            

C)                         21.96 N            

D)                         294.3 N            

Correct Answer: D

Solution :

                      For limiting condition \[f=\mu R\]             \[F\sin 30{}^\circ =\mu (mg-F\cos 30{}^\circ )\], By solving \[F=294.3\ N\]