A block-and-tackle system is used to lift a load of 20N through a vertical height of 10m. if the efficiency of the system is 40%, how much work is done against friction?

Sammyporsche123

3 years ago

correct

Ladykayy

1 year ago

No video explanation so how do I get it 😔

azekah

1 year ago

this is physics

Quinnnnn

1 year ago

please I don't understand how you got 500

Ay17

7 years ago

wrong.....efficiency = workdone by d machine/workdone on the machine × 100%

Tobilobadeebest

2 years ago

the answer should be 120N
The work done against friction in this block-and-tackle system can be calculated using the efficiency formula:

efficiency = (useful work output )/( total work input)

useful work output= efficiency* total work input

total work input = E *l = force * distance
total work input = 20 * 10 = 200j

recall

useful work output = efficiency * total work input
= 40% * 200
= (4/100) * 200
= 80j

since
workdone against friction = total work input - useful wok output
= 200j - 80j = 120j


final answer = 120j

deebest

work done against friction = total work input - useful work output