IB Physics Gravitational Force Between Objects

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This tutorial sheet is on the gravitational force between two objects.

  1. Two solid spheres of masses M1 and M2 uniform density and radii R1 and R2 have their centres a distance r apart (r > R1 + R2).Find the gravitational force acting on each mass.
  2. A uniform spherical shell has a mass M and a radius R. i. What is the gravitational field strength at the centre of the shell? ii. A particle is placed at the centre of the shell and given an initial speed u. Find the time taken to reach the shell.
  3. A uniform rod of mass M and length L is in the same straight line as another uniform rod of mass M and length L. The distance between the centres of the rods is 2L. i. Can we find the attraction between the rods by considering each rod to be a point particle of mass M at its centre of mass? ii. Show that the attraction between the rods is GM2/L2 ln(4/3)