Question

A block and tackle system has 4 pulleys and all is 90% efficient. Calculate
i) Mechanical Advantage
ii) Effort needed to lift a load of 200N
iii) Resistance due to movable parts and friction of pulley system
iv) Is the machine an ideal machine? Justify.

Answer 1

Explanation:

Number of pulleys n = 4.

∴ V.R = 4

η = 90% = 90/100.

(i) Mechanical Advantage :

(M.A)/4 = 90/100

M.A = 3.6

(ii)

Given,

Load = 200 N.

Load/Effort = M.A

⇒ 200/Effort = 3.6

⇒ 200/3.6 = Effort

Effort = 55.5 N

(iii)

Let x be the resistance due to movable parts of machine and friction.

∴ M.A = V.R = x/E

⇒ 3.6 = 4 - x/E

⇒ x = E(4 - 3.6)

⇒ x = E(0.4)

⇒ x = 55.5(0.4)

⇒ x = 22.2N

Therefore,

Resistance = 22.2 N

(iv)

No

Hope it helps!