As Halley’s comet orbits the sun, its distance from the sun changes dramatically. If the comet’s speed at a distance of 9.3 × 1010 m from the sun is 5.1 × 104 m/s and angular momentum is conserved, what is its speed when it is 4.0 × 1012 m from the sun?

Its speed is .

Explanation:

The angular momentum is defined as:

(1)

Since there is no torque acting on the system, it can be express in the following  way:

  (2)

Replacing equation 1 in equation 2 it is gotten:

(3)

As can be seen in equation 3 the angular momentum is conserved.

Where m is the mass of the comet, is the orbital radius when it is farther form the Sun, is the speed when is farther from the Sun, is the orbital radius when is closer to the Sun, is the speed when it is closer to the Sun.

From equation 3 will be isolated:    

  (4)

Hence, its speed is .

e) none of the above answers are correct