The Earth $E$ moves in an elliptical orbit with the Sun $S$ at one of the foci as shown in the figure. Its speed of motion will be maximum at the point:

$A$ stone tied to a string of length $L$ is whirled in a vertical circle,with the other end of the string at the center. At a certain instant of time,the stone is at its lowest position and has a speed $u$. The magnitude of the change in its velocity as it reaches a position where the string is horizontal is

When a big drop of water is formed from $n$ small drops of water,the energy loss is $3E$,where $E$ is the energy of the bigger drop. If $R$ is the radius of the bigger drop and $r$ is the radius of the smaller drop,then the number of smaller drops $(n)$ is:

What type of plants are Pteridophytes?

Which one of the following oxides is reduced by water gas to obtain the metal during its extraction?

$\frac{\sin 1^{\circ}+\sin 2^{\circ}+\ldots+\sin 89^{\circ}}{2(\cos 1^{\circ}+\cos 2^{\circ}+\ldots+\cos 44^{\circ})+1} = $