Given: G = 6.67259 × 10-11 N m2/kg2 After a supernova explosion, a star may un-

Question

Given: G = 6.67259 × 10-11 N m2/kg2 After a supernova explosion, a star may un- dergo a gravitational collapse to an extremely dense state known as a neutron star, in which all the electrons and protons are squeezed to- gether to form neutrons. A neutron star hav- ing a mass of 1.9 × 1030 kg (about equal to that of the Sun) would have a radius of about
14.4 km.
Find the free-fall acceleration at its surface. Answer in units of m/s2

Find the weight of a 39.7 kg person at its surface.
Answer in units of N

Find the energy required to remove a particle
of mass 1.47 × 10-27 kg from its surface to infinity.
Answer in units of J

Explanation / Answer

Part A)

Equating the weight of an object on the surface to the Gravitational Force, we get

mg = GMm/R2

g = GM/R2

g = (6.67259 X 10-11)(1.9 X 1030)/(14400)2

g = 6.11 X 1011 m/s2

Part B)

W = mg = (39.7)(6.11 X 1011) = 2.43 X 1013 N

Part C

W = PE

The enegry required would be equal to the work you would have to do.

The formula for PE is mgh

If you take the height to infinity, the PE is infinite, and therefore the amount of energy required would also be infinite.

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