Question

in a single fixed pulley, the velocity ratio is always more than the mechanical advantage.give reasons.

Answer 1

HELLO THERE!

In a single fixed pulley, the Velocity Ratio is practically always more than Mechanical advantage.

For a pulley,

Mechanical Advantage (M.A) = Load/Effort

Velocity Ratio:

$V.R = \frac{d_{E}}{d_{L}}$

(Where dE = Distance moved by Effort and dL = distance moved by load).

Now,

Efficiency = Work output / Work input

$= \frac{L\times d_{L}}{E \times d_{E}}$

$= \frac{L}{E} \times \frac{d_{L}}{d_{E}} \\\\\implies Efficiency= \frac{MA}{VR}$

Now, for a practical single fixed pulley,

Efficiency is always less than one.

So,

$\frac{MA}{VR} < 1 \\\\\implies MA < VR$

So, it proves that for a practical single fixed pulley, the mechanical advantage is less than Velocity ratio.

Practically speaking, Velocity ratio for a given machine is always same, be the pulley frictionless or with friction. But, when the pulley has some friction (in practical case), you need to give some more effort to overcome the same amount of load, leaving the Velocity ratio unchanged.

When Effort is More than Load,

E > L,

MA = L/E becomes less (bigger number in the denominator makes the whole expression smaller).

So, MA becomes less than VR.

HOPE THIS HELPS...

Thanks!

Answer 2

Answer:

why in a single fixed pulley the velocity ratio is always more than the mechanical advantage. ... Thus effort is able to lift less load than actual effort applied and hence mechanical advantage is less than 1.