G Field

Question 1

Newton’s law of gravitation

Answer 1

The force of attraction between any two point masses is directly proportional to the product of their masses and inversely proportional to the square of their distances apart
F=GMm/r^2
(Sometimes -ve sign in front->to indicative attractive nature of the force as positive direction is taken as the direction of increasing distance)

Question 2

Kepler’ third law

Answer 2

(Note:only can be used if same mass)

T^2 proportional to r^3

Question 3

Gravitational field strength

Answer 3

Gravitational force per unit mass acting on a small mass placed at that point
g=F/m =GM/r^2

Question 4

Gravitational potential energy

Answer 4

Work done by external agent in bringing the mass from infinity to that point
U=-Gmm/r
(-ve since force by external agent is opposite in direction to displacement of mass )

Question 5

Gravitational potential at a point

Answer 5

Work done per unit mass by an external agent in bringing a mass from infinity to that point

Question 6

Relationships

Answer 6

F=-dU/dr

E=-dV/dr

Question 7

Graphs

Answer 7

Pic

Question 8

R/s between KE and PE

Answer 8

Magnitude of KE=half of magnitude of PE

Pic