IB Physics Questions on Gravitation (core)
1. A spherical planet of uniform density has three times the mass of the Earth and twice the
average radius. The magnitude of the gravitational field strength at the surface of the Earth is
g.
What is the gravitational field strength at the surface of the planet?
A. 6g B. C. D.
(Total 1 mark)
2. A spacecraft travels away from Earth in a straight line with its motors shut down. At one
instant the speed of the spacecraft is 5.4 km s–1. After a time of 600 s, the speed is 5.1 km
s–1. The average gravitational field strength acting on the spacecraft during this time interval
is
A. 5.0 × 10–4 N kg–1 B. 3.0 × 10–2 N kg–1 C. 5.0 × 10–1 N kg–1 D. 30 N kg–1
(Total 1 mark)
3. The weight of an object of mass 1 kg at the surface of Mars is about 4 N. The radius of Mars
is about half the radius of Earth. Which of the following is the best estimate of the ratio
below?
A. 0.1 B. 0.2 C. 5 D. 10 (Total 1 mark)
4. Which of the following is true about gravitational field lines?
A. They are always tangential to equipotential surfaces.
B. They are always perpendicular to equipotential surfaces.
C. They can be both tangential or perpendicular to equipotential surfaces.
D. They can have any angle to the equipotential surfaces. (Total 1 mark)
5. Which of the following is true about the gravitational potential V due to a point mass at a
distance r from the point mass?
A. V and always positive B. V and always negative
C. V and always positive D. V and always positive
(Total 1 mark)
, 6. An astronaut in orbit around Earth is said to be “weightless”. This is due to the fact that the
A. gravitational force on the astronaut is zero.
B. astronaut and the spacecraft experience the same acceleration.
C. astronaut and the spacecraft experience the same gravitational force.
D. gravitational field at the position of the spacecraft is zero.
(Total 1 mark)
7. The mass of a planet is twice that of Earth. Its radius is half that of the radius of Earth. The
gravitational field strength at the surface of Earth is g. The gravitational field strength at the
surface of the planet is
A. . B. g. C. 2g. D. 8g.
(Total 1 mark)
8. The mass of Earth is ME, its radius is RE and the magnitude of the gravitational field strength
at the surface of Earth is g. The universal gravitational constant is G. The ratio is equal
to
A. B. C. MERE D. 1
(Total 1 mark)
9. A small sphere X of mass M is placed a distance d from a point mass. The gravitational force
on sphere X is 90 N. Sphere X is removed and a second sphere Y of mass 4M is placed a
distance 3d from the same point mass. The gravitational force on sphere Y is
A. 480 N. B. 160 N. C. 120 N. D. 40 N.
(Total 1 mark)
10. In Newton’s universal law of gravitation the masses are assumed to be
A. extended masses.
B. masses of planets.
C. point masses.
D. spherical masses.
(Total 1 mark)
1. A spherical planet of uniform density has three times the mass of the Earth and twice the
average radius. The magnitude of the gravitational field strength at the surface of the Earth is
g.
What is the gravitational field strength at the surface of the planet?
A. 6g B. C. D.
(Total 1 mark)
2. A spacecraft travels away from Earth in a straight line with its motors shut down. At one
instant the speed of the spacecraft is 5.4 km s–1. After a time of 600 s, the speed is 5.1 km
s–1. The average gravitational field strength acting on the spacecraft during this time interval
is
A. 5.0 × 10–4 N kg–1 B. 3.0 × 10–2 N kg–1 C. 5.0 × 10–1 N kg–1 D. 30 N kg–1
(Total 1 mark)
3. The weight of an object of mass 1 kg at the surface of Mars is about 4 N. The radius of Mars
is about half the radius of Earth. Which of the following is the best estimate of the ratio
below?
A. 0.1 B. 0.2 C. 5 D. 10 (Total 1 mark)
4. Which of the following is true about gravitational field lines?
A. They are always tangential to equipotential surfaces.
B. They are always perpendicular to equipotential surfaces.
C. They can be both tangential or perpendicular to equipotential surfaces.
D. They can have any angle to the equipotential surfaces. (Total 1 mark)
5. Which of the following is true about the gravitational potential V due to a point mass at a
distance r from the point mass?
A. V and always positive B. V and always negative
C. V and always positive D. V and always positive
(Total 1 mark)
, 6. An astronaut in orbit around Earth is said to be “weightless”. This is due to the fact that the
A. gravitational force on the astronaut is zero.
B. astronaut and the spacecraft experience the same acceleration.
C. astronaut and the spacecraft experience the same gravitational force.
D. gravitational field at the position of the spacecraft is zero.
(Total 1 mark)
7. The mass of a planet is twice that of Earth. Its radius is half that of the radius of Earth. The
gravitational field strength at the surface of Earth is g. The gravitational field strength at the
surface of the planet is
A. . B. g. C. 2g. D. 8g.
(Total 1 mark)
8. The mass of Earth is ME, its radius is RE and the magnitude of the gravitational field strength
at the surface of Earth is g. The universal gravitational constant is G. The ratio is equal
to
A. B. C. MERE D. 1
(Total 1 mark)
9. A small sphere X of mass M is placed a distance d from a point mass. The gravitational force
on sphere X is 90 N. Sphere X is removed and a second sphere Y of mass 4M is placed a
distance 3d from the same point mass. The gravitational force on sphere Y is
A. 480 N. B. 160 N. C. 120 N. D. 40 N.
(Total 1 mark)
10. In Newton’s universal law of gravitation the masses are assumed to be
A. extended masses.
B. masses of planets.
C. point masses.
D. spherical masses.
(Total 1 mark)
