A block and tackle system of pulleys consisting of 4 pulleys is used to raise a load of 50N through a height of 20m

If the total workdone against friction in the pulleys is equivalent to 800j
Calculate
I.Total workdone by the effort
ii.The efficiency of the system
iii.The effort applied.

I. (m * g * h) + 800 j

ii. (m * g * h) / [(m * g * h) + 800 j]

iii. (m * g) / {(m * g * h) / [(m * g * h) + 800 j]}

How?

To calculate the values, we can use the formulas:

I. Total work done by the effort = Work done against friction + Work done lifting the load
II. Efficiency of the system = (Work done lifting the load / Total work done by the effort) * 100%
III. Effort applied = Load / Mechanical Advantage

First, let's calculate the mechanical advantage of the block and tackle system. In a system with 4 pulleys, each strand of rope contributes a mechanical advantage of 2. So, the total mechanical advantage is 2 * 2 * 2 * 2 = 16.

Now we can calculate the answers to the given questions:

I. Total work done by the effort = Work done against friction + Work done lifting the load
Total work done by the effort = 800 J + (50 N * 20 m)
Total work done by the effort = 800 J + 1000 J
Total work done by the effort = 1800 J

II. Efficiency of the system = (Work done lifting the load / Total work done by the effort) * 100%
Efficiency of the system = (1000 J / 1800 J) * 100%
Efficiency of the system = 55.6% (rounded to one decimal place)

III. Effort applied = Load / Mechanical Advantage
Effort applied = 50 N / 16
Effort applied = 3.125 N (rounded to three decimal places)

So, the answers are:
I. Total work done by the effort = 1800 J
II. Efficiency of the system = 55.6%
III. Effort applied = 3.125 N

To calculate the total work done by the effort, you need to know the formula for calculating work. Work is equal to force multiplied by distance traveled. In this case, the force is the effort applied, and the distance is the height the load is raised.

i. Total work done by the effort:
The force applied (effort) is the same as the load being lifted, which is 50N. The distance traveled is 20m.

Total work done by the effort = Force * Distance
Total work done by the effort = 50N * 20m
Total work done by the effort = 1000J

Therefore, the total work done by the effort is 1000J.

ii. Efficiency of the system:
Efficiency is defined as the ratio of useful work output to the total work input. To calculate efficiency, we need to compare the useful work (work done against gravity) to the total work input (work done against friction + work done against gravity).

Useful work output = Work done against gravity = Load lifted * Height
Useful work output = 50N * 20m = 1000J (same as total work done by the effort)

Total work input = Work done against friction + Work done against gravity
Total work input = 800J + 1000J = 1800J

Efficiency of the system = (Useful work output / Total work input) * 100%
Efficiency of the system = (1000J / 1800J) * 100%
Efficiency of the system ≈ 55.56%

Therefore, the efficiency of the system is approximately 55.56%.

iii. Effort applied:
The effort applied is the force needed to overcome the load and the friction in the pulley system. We can find it using the work equation and rearranging it:

Total work done against friction + Total work done against gravity = Total work done by the effort

Effort applied = (Total work done by the effort - Total work done against gravity) / Distance
Effort applied = (1000J - 800J) / 20m
Effort applied = 200J / 20m
Effort applied = 10N

Therefore, the effort applied is 10N.