Talha asked in Science & MathematicsPhysics · 2 months ago

Physics Grade 12 help?

When a star like the sun has exhausted most of its fuel, it expands into a red giant with a radius approximately equal to the orbit of Earth, An increase of about 216 times. By what factor does its surface gravity change, assuming mass remains constant.

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  • F = G * m * M / r^2

    F[1] / F[2] = (G * m * M / r[1]^2) / (G * m * M / r[2]^2)

    F[1] / F[2] = r[2]^2 / r[1]^2

    r[2] = 216 * r[1]

    F[1] / F[2] = (216 * r[1])^2 / r[1]^2

    F[1] / F[2] = 216^2 * r[1]^2 / r[1]^2

    F[1] / F[2] = 216^2

    F[1] = 216^2 * F[2]

    F[1] = 46656 * F[2]

    The original force if 46656 times greater than the new force on the surface.  That is, when the sun expands, the force decreases by a factor of 46656.  Something that weighs 46656 pounds on the surface of the sun today would weigh 1 pound on the expanded surface when the radius of the sun increases by a factor of 216

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