A star has a mass of 1.48 x 1030 kg and is moving in a circular orbit about the center of its galaxy. The radius of the orbit is 1.9 x 104 light-years (1 light-year = 9.5 x 1015 m), and the angular speed of the star is 1.8 x 10-15 rad/s. (a) Determine the tangential speed of the star. (b) What is the magnitude of the net force that acts on the star to keep it moving around the center of the galaxy?

a)

3.25 x 10⁵ m/s

b)

8.7 x 10²⁰ N

Explanation:

(a)

w = angular speed of the star = 1.8 x 10⁻¹⁵ rad/s

r = radius of the orbit = 1.9 x 10⁴ ly = 1.9 x 10⁴ (9.5 x 10¹⁵) m = 18.05 x 10¹⁹ m

tangential speed of the star is given as

v = r w

v = (18.05 x 10¹⁹) (1.8 x 10⁻¹⁵)

v = 32.5 x 10⁴ m/s

v = 3.25 x 10⁵ m/s

b)

m = mass of the star = 1.48 x 10³⁰ kg

Net force on the star to keep it moving is given as

F = m r w²

F = (1.48 x 10³⁰) (18.05 x 10¹⁹) (1.8 x 10⁻¹⁵) ²

F = 8.7 x 10²⁰ N