$X$-rays are used in:

$BF_3$ is used as a catalyst in many industrial processes because of its .....

The moment of inertia of a sphere (mass $M$ and radius $R$) about its diameter is $I$. Four such spheres are arranged as shown in the figure. The moment of inertia of the system about the axis $XX'$ will be (in $,I$)

$A$ roller coaster is designed such that riders experience "weightlessness" as they go round the top of a hill whose radius of curvature is $20 \, m$. The speed of the car at the top of the hill is between

An ovule which becomes curved so that the nucellus and embryo sac lie at a right angle to the funicle is called:

Which of the following cereals is a pseudo-cereal?