Two uniform solid spheres of equal radii R, but mass M and 4M have a centre to centre seperation 6R.The two spheres are held fixed.A projectile of mass m is projected from the surface of the sphere of mass M directly towards the centre of the second sphere. Obtain an expression for the minimum speed v of the projectile so that it reaches the surface of the second sphere.
some one pls explain the solution...... i can't understand it clearly...
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3 Answers
See, When you fire the projectile from the surface along the line joining their centers , it experiences force if gravitation from the two spheres as a result of which it has some deceleration [Note that forces on it are unequal] . At some point P on this line, the Field Intensity due to both the spheres is equal. Now just when it crosses that point, it is automatically attracted towards the bigger sphere.
So, In conclusion you need to provide only that much energy so that the particle could just cross the Point P.
Means we only have to find the energy difference between initial point and the point P ?