A block and tackle consisting of 5 pulleys is used to raised a load of 400N through a height of 10m. If the work done against friction is 100j. Calculate;
1)The work done by the effort
2)The efficiency of the system
3)The effort applied

1) 4000Joules

2) 25%

3) 320N

Explanation:

A block and tackle consisting of 5 pulleys is used to raised a load of 400N through a height of 10m.If the work done against friction is 100j.

Calculate;

1)The work done by the effort

2)The efficiency of the system

3)The effort applied

1) Workdone by the effort is the work input = Load * distance moved by the Load

Workdone by the effort = 400 * 10

Workdone by the effort = 4000Joules

2) Efficiency = Work output/Work input * 100

Work output = work done against friction = 100 Joules

Efficiency = 100/4000 * 100

Efficiency = 10000/4000

Efficiency  = 25%

Hence the Efficiency of the system is 25%

3) Using the efficiency formula:

efficiency = MA/VR * 100

Velocity ratio = 5

MA = Load/Effort

efficiency = (L/E)/5 * 100

25 = 400/E/5 * 100

25/100 = 400/5E

0.25 = 400/5E

0.25 * 5E = 400

1.25E = 400

E = 400/1.25

E = 320N

hence the effort applies is 320N