Download Gravitational Problems

Gravitation Problems
Mass of Sun
Radius of Earth
Mass of Moon
Earth-moon distance
Big “G”
2 x 1030 kg
6378 km
7 x 1022 kg
3.82 x 108 m
6.67 x 10-11
Mass of Earth
Light-year
Radius of Moon
Earth-Sun distance
6 x 1024 kg
9.46 x 1015 m
1738 km
1.5 x 1011 m
1. An astronaut weighs 640 N on the earth’s surface. (a) What is the astronaut’s mass? (b) What would she
weigh on the moon? (c) What would she weigh in her spacecraft orbiting at twice the earth’s radius?
(a) 65.3 kg; (b) 101 N; (c) 161 N
2. Oscar, whose mass is 65 kg, and Olivia, whose mass is 45 kg, sit 2.0 m apart in their physics classroom. What is
the gravitational force between them?
4.8 x 10-8 N
3. Our galaxy, the Milky Way, contains approximately 4.0 x 10 11 stars with an average mass of 2 x 1030 kg each.
Assuming that the Andromeda Galaxy has roughly the same number of stars and attracts our galaxy with a force
of 2.4 x 1030 N, determine the distance between our galaxy and the Andromeda Galaxy.
4.2 x 1021 m
4. Calculate the net gravitational force on the earth from the sun and the moon (a) during a full moon and (b)
during a new moon.
(a) 3.54 x 1022 N; (b) 3.58 x 1022 N
5. Jupiter has a mass 318 times that of Earth and a volume that is 1323 times greater than Earth’s. Calculate the
gravitational force exerted on a 50 kg mass on Jupiter’s surface.
1293 N
6. You stand on a spherical, airless asteroid that you know has a radius of 65 km. When you drop a feather, it
falls 45 cm in the first second of fall. What is the mass of the asteroid?
5.7 x 1019 kg
7. A typical neutron star may have a mass equal to that of the Sun but a radius of only 10 km. (a) How much
would a 1 kg rock weigh on the surface of that star? (b) If you dropped the rock from rest, what would its
acceleration be? (c) How fast would the rock be moving after it had fallen 1.0 m?
(a) 1.3 x 1012 N; (b) 1.3 x 1012 m/s/s; (c) 1.6 x 106 m/s
8. One of the Echo satellites consisted of an inflated spherical aluminum balloon 30 m in diameter and of mass 20
kg. Suppose a meteor having a mass of 7.0 kg passes within 3.0 m of the surface of the satellite. What is the
magnitude of the gravitational force on the meteor from the satellite at the closest approach?
2.9 x 10-11 N
9. Compare the gravitational force exerted on a 3 kg baby (a) by a 70 kg obstetrician who is 1 m away (and
approximated as a point mass), (b) by the planet Jupiter (2 x 10 27 kg) at its closest approach to earth (6 x 1011 m),
and (c) by a Sun-like star 10 light-years away.
(a) 1 x 10-8 N; (b) 1 x 10-6 N; (c) 4.5 x 10-14 N
10. A spaceship is on a straight-line path between Earth and its moon. At what distance from Earth is the net
gravitational force on the spaceship zero?
3.44 x 108 m