• QUESTIONS BEFORE LECTURE 8

now think about these

• What is the meaning of "universal" in Newton's Universal Law of Gravity?
• What is meant by the statement "the moon is falling?"
• What property determines whether a projectile will fall to the earth or go into orbit around the earth?
• Why does the force of gravity depend on one mass?
• Why does the force of gravity depend on the other mass, too?
• Why does the force of gravity depend on the inverse square of the distance between masses, instead of the distance or inverse distance, for example? The answer is a plausibility argument.
• Why is the constant G needed in the force formula?
• Why do we say the mass in Newton's 2nd Law is "inertial" mass and in Newton's Law of Gravitation is "gravitational" mass, when they are the same mass?
• How can the weakest force in nature hold the whole universe together?