A planet moves around the Sun in an elliptical orbit (see Fig. 8.40). 

(a) Show that the external torque acting on the planet about an axis through the Sun is zero. 

(b) Since the torque is zero, the planet's angular momentum about this axis is constant. Write an expression for the planet's angular momentum in terms of its mass m, its distance r from the Sun, and its angular velocity ω. 

(c) Given r and ω, how much area is swept out during a short time Δt?

Transcribed Image Text:

Sun Sun Planet Perihelion Aphelion (a) (b)