Question

Gravitation newton's laws of gravitation,newton's gravitational constant (g) and its si unit, acceleration due to gravity (g) and its relation with "g",variation of g with altitude and latitude(deduction not required)

Answer 1

N's 1st law A body always remains in its state until a force is not act on it. #########. # N's 2nd law change in linear momentum is directly proportional to force .

F = dp/dt =dmv/dt { p = mv } # F = mdv/dt = ma { dv/dt = a} # N's 3rd law each action has always equal and opposite reaction .for ex. when a bullet is fired gun exert forward force and bullet also exert backward force .that is why a gun move back during firing.

Answer 2

Newton 1st law : If a body is at rest it will remain at rest and if a body is in motion, it will remain in motion until an external force is not applied on it .
Newton's Second law : Rate of change of momentum is directly proportional to the force applied on the body.
Newton's 3rd law : Every action has an equal and opposite reaction.
It's SI unit is m/s^2.
Acceleration due to gravity : Whenever an object falls towards the earth an acceleration is involved. This acceleration is called gravitational acceleration.
Relation b/w g and G :
Let mass of earth = M
Mass of object placed at surface of earth = m
earth = m
Radius of earth = R
According to Universal Law of Gravitation
F = GMm/R^2........eq(1)
According to 2nd law of motion
F = mg........eq(2)
By (1) & (2)
mg = GMm/R^2
g = GM/R^2.