Find the potential energy of a system of four particles placed at the vertices of a square of side l. also, obtain the potential at the centre of the square.

consider a sqaure ABCD,and centre O

OA=1/2 AC =1/2 I root2 = I/root2

OA=OB=OC=OD=I/root2

Total potential energy = -2Gm2/I [ 2 + 1/root2]

= -5.414Gm2/I

Consider four masses each of mass m at the corners of a square of side ; See  Figure.

We have four mass pairs at distance and two diagonal pairs at distance

   Hence,

The gravitational potential at the centre of the square is

answer

Explanation:The P.E of 4 vertices must be substracted from the P.E between the diagonals

it should be the answer

potential energy = GX M X m/(R+h)

for 4 particles,

E= G X M X m/[{2+(R+h)} + {2/R + I + h}]

if particle is at centre of square

E= (G X M X m)/( R + h + 0.5 X I)

cracks in solids spread at a characteristic speed.

answer:

54000

explanation:

1500(72-36)

1500*36

54000