🚀 go-pugleaf

Hi, if anyone can help by answering some of the Questions below we would be
most grateful. We have attempted them all, but are unsure of the correct
answers.

***
A steel rod, of length 2.0m, is at a distance of 5.0*10^5 m from the center
of a black hole of mass 1.8*10^31 kg and is falling towards it.
By considering the forces acting on the two halves A and B of the rod,
estimate the stress at the center of the rod. Assume that the forces act,
respectively, at the planes of the centroids of the two halves.
- You may make use of the approximation {1/r^2 - 1/(1+ dr)^2} = 2dr / r^3  
---   d=delta
- Density of Steel = 7.8*10^3 kg m^-3
- Grav. Constant = 6.7*10^-11 N Kg^-2 m^2
***

***
An object of mass X collides (traveling with velocity v) with an isolated
heavier, stationary object of mass Y, and becomes embedded in it.
(i) Show, with the aid of a calculation involving X, Y and v, that although
the total momentum of the objects is unchanged by the collision, their
total kinetic energy decreases.
(ii) Explain how the principle of conservation of energy can be applied to
this collision.
***

***
A spacecraft is equipped with solar panels with a total area of 30 m^2. The
panels are stabilized so that the rays from the Sun always fall normally on
them. If the Sun radiates uniformly in all directions at a power of
3.9*10^26 W, calculate the power received by the panels when the spacecraft
is at a distance of 220 * 10^6 km from the Sun.
***

Thanks in advance to anyone who can help.