Question

A screw jack has a thread of 10mm pitch, length of handle is 400mm. calculate effort applied p to lift a load of 2kN is efficiency of screw jack is 45%.​

Answer 1

Given that,

Thickness = 10 mm

Length =400 mm

Load = 2kN

Efficiency = 45%

We need to calculate the velocity ratio

Using formula of velocity ratio

$V.R=\dfrac{2\pi l}{p}$

Where, p = pitch of thread

l = length

Put the value into the formula

$V.R=\dfrac{2\pi\times400\times10^{-3}}{10\times10^{-3}}$

$V.R=251.32$

We need to calculate the M.A

Using formula of M.A

$M.A=\dfrac{W}{P}$

Where, W = load

P = Effort required to lift the load

Put the value into the formula

$M.A=\dfrac{2000}{P}$

We need to calculate the effort applied

Using formula of efficiency

$\eta=\dfrac{M.A}{V.R}$

Put the value into the formula

$0.45=\dfrac{\dfrac{2000}{P}}{251.32}$

$P=\dfrac{2000}{0.45\times251.32}$

$P=17.7\ N$

Hence, The applied effort is 17.7 N.