Question

Suppose that the radius of the earth becomes twice of its original radius without any change in its mass, then what change will you note in your weight? Justify your answer.State the universal law of gravitation. What is the value of G?Define momentum. What is the SI unit of momentum? Calculate the momentum of a toy car weighing 200g and moving with a velocity of 5ms-1.

Answer 1

Given:
1)g=GM/R²
R is  doubled.
R=2R
g1=GM/2R²
g1=GM/4R²
g1=g/4
so new gravitation will be g/4
our weight will be 1/4 times of previous weight.
ii)The universal law of gravitation states that every object in the universe attracts every other object with a force called the gravitational force. The force acting between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centres.
For two objects of masses m1and m2 and the distance between them r, the force (F) of attraction acting between them is given by the universal law of gravitation as:

F=Gm1m2/R²
where G is the universal constant . its value is 6.6.7 x 10-11 Nm2/KG2
3)Momentum: Momentum is the product of velocity and its mass
p=mxv
its units are Kg-m/s or N-s
to calculate momentum of toy car:
given m=200g=200/1000=0.2 kg
v=5m/s
p=0.2x5
=1 Kg-m/s