When a star like our sun runs out of nuclear fuel, it collapses to a white dwarf star the size of the Earth, but with the same mass the star had before the collapse. If a star initially rotates once every 25 days, like our sun, what will its rotation rate be after it becomes a dwarf

T = 1.8 10² s

Explanation:

This is an exercise of conservation of angular momentum,

Initial instant. Before collapsing

         L₀ = I₀ w₀

Final moment. After the collapse

         L_f = I w

as the system is isolated, the moment is conserved

         L₀ = L_f

         I₀ w₀ = I w

         w =

indicates that the rotation period is 25 day, let's reduce to the SI system

        T = 25 day (24 h / 1 day) (3600 s / 1 h) = 2.16 10⁶ s

     Angular velocity and period are related

       w = 2π/ T

The moment of inertia of a sphere is

        I = 2/5 M R ²

in this case the moment before and after the collapse is

       I₀ = 2/5 M R₀²

       I = 2.5 M R²

the radius of a star like the sun is

      R₀ = 6.96 10⁸ m

the radius of the earth

      R = 6.371 10⁶ m

we substitute

     w =  

      T = ( )² T₀

let's calculate

    T = (6.371 10⁶ / 6.96 10⁸ )² 2.16 10⁶

    T = 1.8 10² s

there are no correct statementd on the list of choices you provided.

laticia draws the diagram below to show earth’s magnetic field.

answer

the arrows to the right of earth should point up.