You wish to lift a 400 lb car engine a vertical distance of 3 ft using a strong rope. Unfortunately, your hand crank winch can only generate 100 lb of tension in your rope. In order to overcome this obstacle, you use a multiple pulley system (block and tackle) to lift the engine.

a)What is the mechanical advantage of this system?

b) What length of rope is required to complete the work?

Explanation:

a) Mechanical Advantage is defined as the ratio of the load to the effort applied to an object. Mechanical advantage occurs when we can use a minimal effort to overcome a much larger load.

Mathematically; Mechanical advantage = Load/ Effort

Load =  400 lb car engine

Effort applied = Tension generated by the hand crank in the rope = 100lb

Mechanical Advantage = 400lb/100lb

MA = 4

b) Assuming the efficiency is 100%

Efficiency = Workdone by the machine/Work put in the machine * 100%

Workdone by the machine = work output = Force * distance moved by load

= 400*3

= 1200lbft

Work put in the machine = Work input = Force * distance moved by effort

Work input = 100*d

substituting into the equation;

100% = 1200/100d * 100%

1 = 1200/100d

100d = 1200

d = 1200/100

d = 12ft

The length of the rope required to complete the work is 12ft

what is the actual question though?