The upper surface of an aluminium cube of side 10 cm is displaced by 0.03 cm with respect to its firmly held lower surface by a tangential force of `7.5 times 10^10 dyn`. Calculate the modulus of rigidity of aluminium.

Explanation

Modulus of rigidity, `n=F/(A theta )`
Here, `F=7.5times10^10dyn,A=10times10=100cm^2`
`theta=0.03/10=0.003`
`therefore` Modulus of rigidity,
`n=(7.5times10^10)/(100times0.003)`
`=2.5 times10^11dyn.cm^-2`
`=2.5 times10^10N.m^-2`