250 N force is required to raise 75 kg mass from a pulley. If rope is pulled 12 m then the load is l

Question

250 N force is required to raise 75 kg mass from a pulley. If rope is pulled 12 m then the load is lifted to 3 m , the efficiency of pulley system will be\

Professor PC Thomas Classes · Answer

(c): Load $W=M g=75 	imes 10=750 \mathrm{~N}$ Effort $P=250 \mathrm{~N}$\ $	herefore \quad$ Mechanical advantage $$ =\frac{	ext { load }}{	ext { effort }}=\frac{W}{P}=\frac{750}{250}=3 $$ Velocity ratio $$ =\frac{	ext { distance travelled by effort }}{	ext { distance travelled by load }}=\frac{12}{3}=4 $$ Efficiency, $\eta=\frac{	ext { Mechanical advantage }}{	ext { Velocity ratio }}=(3 / 4) 	imes 100=75 \%$.\