An alloy which does not contain copper is

If $x^2+y^2=t-\frac{1}{t}$ and $x^4+y^4=t^2+\frac{1}{t^2}$,then $\frac{dy}{dx}=$

The length of an elastic string is $a$ metre when the longitudinal tension is $4 \ N$ and $b$ metre when the longitudinal tension is $5 \ N$. The length of the string in metre when longitudinal tension is $9 \ N$ is

If a change in current of $0.01 ~A$ in one coil produces a change in magnetic flux of $2 \times 10^{-2} ~Wb$ in the other coil,then the mutual inductance of the two coils in henry is (in $~H$)

The monomer $( X )$ involved in the synthesis of Nylon $6,6$ gives positive carbylamine test. If $10$ moles of $X$ are analyzed using Dumas method, the amount $($in grams$)$ of nitrogen gas evolved is $....$
Use: Atomic mass of $N ($in amu$) = 14$

From a solid sphere of mass $M$ and radius $R$,a cube of maximum possible volume is cut. The moment of inertia of the cube about an axis passing through its centre and perpendicular to one of its faces is