8. Centripetal Forces & Gravitation

Which of the following best describes what is meant when we say that the $\mathrm{Sun}$ is in gravitational equilibrium?

Which of the following best explains why the north pole of a compass needle points toward Earth's geographic north pole?

Which of the following statements about the force of gravity is false?

Which statement correctly compares the acceleration due to gravity on $Earth$ and on the $Moon$?

According to Newton's Law of Gravity, what is the relationship between the gravitational force $F$ and the masses $m_1$ and $m_2$ of two objects?

Two spheres of mass 300 kg and 500 kg are placed in a line 20 cm apart. If another sphere of mass 200 kg is placed between them, 8 cm from the 300 kg sphere, what is the net gravitational force on the 200 kg sphere?

A 2,000-kg spacecraft is blasting away from the surface of an unknown planet the same size as the Earth. At 1500km above the surface, an instrument onboard reads the gravitational force to be 18000 N. What is the planet's mass?

 Two spheres are separated by 10m. If the lighter 40kg sphere feels a gravitational force of 1.6 × 10^-9 N, what is the mass of the heavier sphere?

(II) You are explaining to friends why an astronaut feels weightless orbiting the Earth in a space station, and they respond that they thought gravity was just a lot weaker up there. Convince them that it isn’t so by calculating how much weaker (in %) gravity is 380 km above the Earth’s surface.

The point masses m and 2m lie along the x-axis, with m at the origin and 2m at x = L. A third point mass M is moved along the x-axis. At what point is the net gravitational force on M due to the other two masses equal to zero?

Find the magnitude and direction of the net gravitational force on mass A due to masses B and C in Fig. E13.6. Each mass is 2.00 kg.

Two uniform spheres, each with mass M and radius R, touch each other. What is the magnitude of their gravitational force of attraction?

Two spherical objects have a combined mass of 150 kg. The gravitational attraction between them is 8.00 x 10^-6 N when their centers are 20 cm apart. What is the mass of each?