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?

a) 4

b) 12 ft

Explanation:

a) The Mechanical advantage = Weight of car / tension in the rope

Given that weight of car = 400 lb and tension in the rope = 100 lb

Therefore, Mechanical advantage = 400 lb / 100 lb = 4

Mechanical advantage = 4

b) The length of the rope = Vertical height × Mechanical advantage

The vertical height = 3 ft

The length of the rope = 3 ft × 4 = 12 ft

energy can cross the boundaries of a closed system in the form of heat and mass

explanation: