Which of the following is a characteristic feature of viruses?

The condition that $f(x)=a x^3+b x^2+c x+d$ has no extreme value,is

When a mass $m$ is connected individually to two springs $S_1$ and $S_2$,the oscillation frequencies are $v_1$ and $v_2$. If the same mass is attached to the two springs as shown in the figure,the oscillation frequency would be

We have two spheres,one of which is hollow and the other solid. They have identical masses and moments of inertia about their respective diameters. The ratio of their radii is given by:

The bob of a simple pendulum is hanging vertically down from a fixed identical bob by means of a string of length $l$. If both bobs are charged with a charge $q$ each,what is the time period of the pendulum? (Ignore the radii of the bobs.)

If $x-y+1=0$ meets the circle $x^2+y^2+y-1=0$ at $A$ and $B$,then the equation of the circle with $AB$ as diameter is