Why are aquatic species more comfortable in cold water than hot water?

An atom of an element has 7 electrons in its L shell.

(a) What is its atomic number?

(b) State its valency.

(c) Identify the element.

A boy throws a ball vertically upwards and catches it back in 10 s. Calculate

(i) the velocity with which it was thrown up and

(ii) maximum height attained by the ball. (Take $\mathrm{g}=10 {\mathrm{ms}}^{-2}$)

A circular track has a circumference of 3140 m with AB as one of its diameter. A scooterist moves from A to B along the circular path with a uniform speed of 10 m/s. Find

(a) distance covered by the scooterist,

(b) displacement of scooterist, and

(c) time taken by the scooterist in reaching from A to B.