Question

Pictured above is a planet in its orbit around a star.
Rank the locations according to the speed of the planet at that location, greatest first:

• A. $1,2,3,4$
• B. $4,3,1,2$
• C. $2,1,3,4$
• D. $3,1,2,4$
• E. At all locations the planet travels at the same speed

Answer 1

Answer: (B)

$4,3,1,2$

From the conservation of energy of the system, the sum of kinetic energy of the planet and the gravitational potential energy of system is constant.

The gravitational potential energy for the different positions is ranked as follows-

$2>1>3>4$

Hence the kinetic energy of planet and hence the speed of planet is ranked as-

$4>3>1>2$

Hence correct answer is option B.