Q1.What are the factors which determine ; Why some bodies in solar system have
atmosphere and others don’t have?
Ans. The ability of a body (planet) to hold the atmosphere depends on acceleration due to gravity.
Q2.Should the speed of two artificial satellites of the earth having different masses but the same orbital radius, be the same?
Ans.Yes it is so because the orbital speed of a satellite is independent of the mass of a satellite. Therefore the speeds of the artificial satellite will be of different masses but of the same orbital radius will be the same.
Q3.Can a pendulum vibrate in an artificial satellite?
Ans. No, this is because inside the satellite, there is no gravity ,
i.e., g=0.
As t = 2π , hence, for g=0 , t = . Thus, the pendulum will not vibrate.
Q4.Why do different planets have different escape speed?
Ans. As, escape speed = , therefore its value are different for different
planets which are of different masses and different sizes.
Q5.Show that weight of all body is zero at Centre of earth?
Ans. The value of acceleration due to gravity at a depth d below the surface of earth
of radius R is given by ɠ=g(1-d/R).At the center of earth, (dept)d=R; so, ɠ =0.The
weight of a body of mass m at the centre of earth =mg’=m x 0=0.
Q6.Why does moon have no atmosphere?
Ans. Moon has no atmosphere because the value of acceleration due to gravity ‘g’
on surface of moon is small. Therefore, the value of escape speed on the surface of
moon is small. The molecules of atmospheric gases on the surface of the moon
have thermal speeds greater than the escape speed. That is why all the molecules
of gases have escaped and there is no atmosphere on moon
Q7.What are the conditions under which a rocket fired from earth, launches
an artificial satellite of earth?
Ans. Following are the basic conditions: (i) The rocket must take the satellite to
a suitable height above the surface of earth for ease of propulsion.
(ii)From the desired height, the satellite must be projected with a suitable
speed, called orbital speed.
(iii)In the orbital path of satellite, the air resistance should be negligible so that
its speed does not decrease and it does not burn due to the heat produced.
Q1.State Kepler’s laws of planetary motion. Prove second Kepler’s law using
concept of conservation of angular motion.
Q2.State universal law of gravitation. What is the significance of this law. Find the
expression for acceleration due to gravity.
Q4. Define gravitational potential energy. Derive the expression for gravitational
potential energy. What is the maximum value of gravitational potential energy?
Q5.What is escape speed? Derive the expressions for it. Calculate escape speed for
the Earth
atmosphere and others don’t have?
Ans. The ability of a body (planet) to hold the atmosphere depends on acceleration due to gravity.
Q2.Should the speed of two artificial satellites of the earth having different masses but the same orbital radius, be the same?
Ans.Yes it is so because the orbital speed of a satellite is independent of the mass of a satellite. Therefore the speeds of the artificial satellite will be of different masses but of the same orbital radius will be the same.
Q3.Can a pendulum vibrate in an artificial satellite?
Ans. No, this is because inside the satellite, there is no gravity ,
i.e., g=0.
As t = 2π , hence, for g=0 , t = . Thus, the pendulum will not vibrate.
Q4.Why do different planets have different escape speed?
Ans. As, escape speed = , therefore its value are different for different
planets which are of different masses and different sizes.
Q5.Show that weight of all body is zero at Centre of earth?
Ans. The value of acceleration due to gravity at a depth d below the surface of earth
of radius R is given by ɠ=g(1-d/R).At the center of earth, (dept)d=R; so, ɠ =0.The
weight of a body of mass m at the centre of earth =mg’=m x 0=0.
Q6.Why does moon have no atmosphere?
Ans. Moon has no atmosphere because the value of acceleration due to gravity ‘g’
on surface of moon is small. Therefore, the value of escape speed on the surface of
moon is small. The molecules of atmospheric gases on the surface of the moon
have thermal speeds greater than the escape speed. That is why all the molecules
of gases have escaped and there is no atmosphere on moon
Q7.What are the conditions under which a rocket fired from earth, launches
an artificial satellite of earth?
Ans. Following are the basic conditions: (i) The rocket must take the satellite to
a suitable height above the surface of earth for ease of propulsion.
(ii)From the desired height, the satellite must be projected with a suitable
speed, called orbital speed.
(iii)In the orbital path of satellite, the air resistance should be negligible so that
its speed does not decrease and it does not burn due to the heat produced.
Q1.State Kepler’s laws of planetary motion. Prove second Kepler’s law using
concept of conservation of angular motion.
Q2.State universal law of gravitation. What is the significance of this law. Find the
expression for acceleration due to gravity.
Q4. Define gravitational potential energy. Derive the expression for gravitational
potential energy. What is the maximum value of gravitational potential energy?
Q5.What is escape speed? Derive the expressions for it. Calculate escape speed for
the Earth
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