A block and tackle containing 3 fixed and 2 movable pulley is used to lift a load of 1200N to a store 15m from the ground if work done in overcoming friction is 6000J calculate work done by the effort,efficiency, effort applied
To calculate the work done by the effort, we first need to determine the total work done on the load. We can do this by calculating the input work, which is the work done in lifting the load, and subtracting the work done in overcoming friction.
1. Calculate the input work:
The input work is equal to the force exerted multiplied by the distance over which the force is applied.
Input work = Force × Distance
Given:
Force = 1200 N (load to be lifted)
Distance = 15 m (height the load is lifted)
Input work = 1200 N × 15 m = 18000 J
2. Calculate the work done by the effort:
The work done by the effort is the same as the input work in an ideal situation. However, since there is work done in overcoming friction, the work done by the effort will be less than the input work.
Work done by the effort = Input work - Work done in overcoming friction
Given:
Work done in overcoming friction = 6000 J
Work done by the effort = 18000 J - 6000 J = 12000 J
Therefore, the work done by the effort is 12000 J.
3. Calculate the efficiency:
The efficiency of a machine is given by the ratio of output work to input work, expressed as a percentage.
Efficiency = (Work done by the effort ÷ Input work) × 100%
Efficiency = (12000 J ÷ 18000 J) × 100% = 66.67%
Therefore, the efficiency of the block and tackle system is 66.67%.
4. Calculate the effort applied:
The effort applied can be determined using the formula:
Effort = (Load × Distance) ÷ Number of movable pulleys
Given:
Load = 1200 N
Distance = 15 m
Number of movable pulleys = 2
Effort = (1200 N × 15 m) ÷ 2 = 9000 N
Therefore, the effort applied is 9000 N.