As observed from the earth, the sun appears to move in an approximately circular orbit. For the motion of another planet like mercury as observed from the earth, this would:
1. | be similarly true. |
2. | not be true because the force between the earth and mercury is not inverse square law. |
3. | not be true because the major gravitational force on mercury is due to the sun. |
4. | not be true because mercury is influenced by forces other than gravitational forces. |
Different points in the earth are at slightly different distances from the sun and hence experience different forces due to gravitation. For a rigid body, we know that if various forces act at various points in it, the resultant motion is as if a net force acts on the centre of mass causing translation and net torque at the centre of mass causing rotation around an axis through the CM. For the earth-sun system (approximating the earth as a uniform density sphere):
1. | the torque is zero. |
2. | the torque causes the earth to spin. |
3. | the rigid body result is not applicable since the earth is not even approximately a rigid body. |
4. | the torque causes the earth to move around the sun. |
Choose the wrong option.
1. | Inertial mass is a measure of the difficulty of accelerating a body by an external force whereas gravitational mass is relevant in determining the gravitational force on it by an external mass. |
2. | That the gravitational mass and inertial mass are equal is an experimental result. |
3. | That the acceleration due to gravity on the earth is the same for all bodies is due to the equality of gravitational mass and inertial mass. |
4. | Gravitational mass of a particle-like proton can depend on the presence of neighbouring heavy objects but the inertial mass cannot. |
Particles of masses 2M, m and M are respectively at points A, B and C with . The mass m is much-much smaller than M and at time t = 0, they are all at rest as given in the figure. At subsequent times before any collision takes place,
1. m will remain at rest.
2. m will move towards M.
3. m will move towards 2M.
4. m will have oscillatory motion.
There have been suggestions that the value of the gravitational constant G becomes smaller when considered over a very large time period (in billions of years) in the future. If that happens, for our earth,
a. | nothing will change |
b. | we will become hotter after billions of years |
c. | we will be going around but not strictly in closed orbits |
d. | after a sufficiently long time, we will leave the solar system |
Choose the correct alternatives:
1. (a, c)
2. (a, d)
3. (c, d)
4. (a, b)