during its orbital period, as a planet moves closer to the sun, the orbital velocity of the planet:?

Question

a. increases
b. decreases
c. remains the same
d. is unpredictable

Answer 1

Increases.

According to Kepler's 3rd law :
r^3 is directly proportional to T^2
When the planet is closer to the sun, r decreases and so Time period decreases.

Hence the orbital velocity increases.

Hope this helps.

[e-mail]

Answer 2

By Kepler's second law
The areal velocity of the planet is a constant.
1/2 r^2 dθ/dt is a constant
dθ/dt = v/r
Therefore 1/2 r^2 * v/r is a constant
vr is a constant.
When r decreases v increases and vice versa.

Answer 3

a. Increases. As a planet gets closer to the sun, it speeds up. The potential energy of teh orbit decreases as the planet nears the sun, so the kinetic energy must increase (total energy is conserved). If kinetic energy increases, the planet must speed up.

Answer 4

The same principle is involved here as when an ice skater spins on the ice with arms outstretched and then brings them closer to her body. The speed increases.