Why is k negative in gravitational force and proof of escape velocity formula?

[hadeel]

1- F = mk/r^2 ... k is -ve value ...why ?? please in concise way


2- for escape velocity ...
v( inital) = root ( 2gR )... with proof

thank u

 

[Doc Al]

1- F = mk/r^2 ... k is -ve value ...why ?? please in concise way

Gravity is an attractive force, which acts in the -r direction.

2- for escape velocity ...
v( inital) = root ( 2gR )... with proof

Prove it for yourself using conservation of energy.