A lot contains $$20$$ articles. The probability that the lot contains exactly $$2$$ defective articles is $$0.4$$ and the probability that the lot contains exactly $$3$$ defective articles is $$0.6$$. Articles are drawn from the lot at random one by one without replacement and are tested till all defective articles are found. What is the probability that the testing procedure ends at the twelth testing.

The dimensions of the quantities in one ( or more ) of the following pairs are the same. Identify the pair(s)

A reference frame attached to the earth

A simple pendulum of length L and mass (bob) M is oscillating in a plane about a vertical line between angular limit $$ - \phi $$ and $$ + \phi $$. For an angular displacement $$\theta $$ $$\left( {\left| \theta \right| < \phi } \right)$$, the tension in the string and the velocity of the bob are T and V respectively. The following relations hold good under the above conditions: