$540\, g$ of ice at $0^\circ C$ is mixed with $540\, g$ of water at $80^\circ C$. The final temperature of the mixture is

Two lenses in contact made of materials with dispersive powers in the ratio $2 : 1$,behave as an achromatic convex lens of focal length $10\, cm$. The individual focal lengths of the lenses are

An object with a mass $10 \ kg$ moves at a constant velocity of $10 \ m/s$. $A$ constant force then acts for $4 \ s$ on the object and gives it a speed of $2 \ m/s$ in the opposite direction. The impulse acting on the object is ........ $N \cdot s$.

Larger number of oxidation states are exhibited by the actinoids than those by the lanthanoids,the main reason being

Membrane-bound organelles are absent in

If the area of an equilateral triangle inscribed in the circle $x^2 + y^2 + 10x + 12y + c = 0$ is $27\sqrt{3}$ sq. units,then $c$ is equal to: