Question

A system with one fixed and one moveable pulley operates with 90% efficiency. The moveable pulley has a weight of 5 N. Using this pulley system, what is the minimum input force needed to lift a piano weighing 1,595 N?

Answer 1

Answer: C. 889 N

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Answer 2

800 N

Step-by-step explanation

Efficiency = (mechanical advantage)/(velocity ratio) × 100%

Mechanical advantage (M.A) = Load/Effort

= (1,595+5)/Effort

= 1,600/Effort

Velocity ratio = 2

90/100 = M.A/2

M.A = 0.9 × 2

= 1.8

M.A = 1,600/Effort

2 = 1,600/Effort

Effort = 1600/2

= 800 N