Physics help please!?

Question

(a) Find the acceleration due to gravity at the surface of a neutron star of mass 1.5 solar masses and having a radius of 11.0 km.
____m/s2
(b) Find the weight of a 0.121 kg baseball on this star.
____N
(c) Assume the equation PE = mgh applies, and calculate the energy that a 70.0 kg person would expend climbing a 1.00 cm tall mountain on the neutron star.
____J

Thank you to everyone that attempts this problem! You are a genius. Everyone in my physics group (including me) does not understand this one. Thanks again!

Answer 1

(a) use the formula for gravitational force and divide out the mass of an arbitrary object:

g=G*m/r^2

where g=acceleration due to gravity on the star, G=universal gravitational constant, m=mass of the star, and r=radius of the star. Find the mass of the sun to be 1.988x10^30 Kg (go look it up). The mass of the star is 1.5 times that m=2.98x10^30 Kg. Put that into the formula and you get:

g=G*2.98x10^30/(1.1x10^4)^2=1.644x10^12 m/sec^2

10^12 is the tera prefix in SI and is denoted by letter T

g=1.644 Tm/sec^2

(b) weight is just mass times acceleration:

w=0.121Kg * 1.644x10^12m/sec^2=1.99x10^11 N

(c) Technically, a 70Kg person on the neutron star would not be climbing any mountains. He'd be dead flat as a pancake against the ground. However, hypothetically speaking, energy expended is just m*g*h

E=(70Kg)*(1.644x10^12 m/sec^2)*(0.01m)=1.15x10^12 J
E=1.15TJ

Lol. Just looked it up. That's equivalent to the total energy output of about 0.27 kilotons or 275,000Kg of TNT. It's a small fission nuclear blast.

Answer 2

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