Question

9. Mechanical advantage of a block and tackle system is 4.

i. Draw the diagram and mark the direction of forces in the strings.

ii. If the frictional force f cannot be neglected, what will be its velocity ratio?

iii. When load is pulled up by a distance of 1 m, how far does the effort end move in ideal

case?

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Answer 1

Given that,

Mechanical advantage of a block and tackle system is 4.

(I). We need to draw a diagram and mark the direction of forces in the strings

According to figure,

Effort is T and mechanical advantage of a block is 4.

Load is 4T.

If the frictional force f cannot be neglected

(II). Under ideal condition.

$M.A = V.R$

We need to calculate the velocity ratio

Using formula of mechanical advantage

$M.A=\dfrac{load}{effort}$

$V.R=\dfrac{load}{effort}$

Put the value into the formula

$V.R=\dfrac{4T}{T}$

$V.R=4$

The velocity ratio is 4.

(III). When load is pulled up by a distance of 1 m

We need to calculate the effort

Using formula for effort

If load is pulled up by a distance 1 m then the effort end moves by 4m.

Hence, (I). Draw the diagram.

(II). The velocity ratio is 4.

(III). The effort end moves by 4m.