Gravity Flashcards
Flashcard 3: Q: How was Galileo’s idea of objects falling at the same rate regardless of mass demonstrated in modern times?
A: In 1971, an astronaut on the Moon dropped a hammer and a feather, and they fell at the same rate in the vacuum of the Moon, proving Galileo right.
Flashcard 2: Q: Why do a feather and a rock not fall at the same rate in normal conditions?
A: Due to air resistance. The feather has a larger surface area relative to its mass, causing air resistance to slow its fall.
Flashcard 4: Q: What observation is necessary for deriving the law of universal gravitation?
A: All objects fall at the same rate regardless of mass.
Flashcard 5: Q: What is Newton’s second law of motion in relation to gravitational force?
A: The gravitational force experienced by an object is directly proportional to its mass. Double the mass, and you double the force.
Flashcard 6: Q: What was Newton’s insight regarding the direction of gravitational pull?
A: Newton wondered why objects always fall towards the center of the Earth and not sideways or upwards. He deduced that gravity pulls objects towards the center of mass.
Flashcard 7: Q: What is Newton’s third law of motion, and how does it apply to gravity?
A: For every action, there is an equal and opposite reaction. This applies to gravity in that if the Earth pulls on the Moon, the Moon pulls back on the Earth with an equal force.
Flashcard 8: Q: What effect does air resistance have on falling objects with different masses but the same shape?
A: The object with greater mass (e.g., a rock) will still fall faster than the lighter object (e.g., a feather) because air resistance has a smaller net effect on the heavier object.
Flashcard 9: Q: What are the three key points Newton needed to derive the law of universal gravitation?
A: 1) All objects fall at the same rate regardless of mass, 2) Every mass attracts every other mass, 3) Objects fall toward the center of mass, not just the surface.
Q: Why can’t alternative mathematical relations (e.g., adding masses or taking square roots) describe the gravitational force between two masses?
A: Only the product of the two masses fits the observation that the force scales directly with each mass. No other relation (e.g., addition or square roots) satisfies this condition.
Q: How did Newton confirm that distance affects the gravitational force between two objects?
A: Newton reasoned that increasing the distance between objects would reduce the gravitational force, and this was later confirmed with accurate measurements of distances, like the Earth-Moon distance.
Q: What is the significance of the distance between objects in the calculation of gravitational force?
A: Gravitational force decreases with the square of the distance between two objects. The farther apart the objects, the weaker the gravitational force.
Q: Why did Newton believe that objects dropped from a height show no significant change in falling speed?
A: The Earth’s radius is so large (6,400,000 meters) that a small change in height (like 30 meters) is negligible, making the gravitational force seem constant within experimental uncertainty.
Q: How was the distance to the moon calculated, and why was this important for understanding gravity?
A: The distance to the moon (384,000 km) was calculated using geometric observations of eclipses. This allowed Newton to use the moon’s distance to solve for the gravitational force between the Earth and the moon.
Q: How does Newton’s concept of orbit demonstrate gravitational force?
A: Newton explained that if an object is thrown hard enough, it will fall around the Earth in an orbit, continuously “falling” but never hitting the surface due to Earth’s curvature.
Q: What did Newton realize about the relationship between the moon’s motion and gravitational force?
A: Newton realized that the moon is constantly “falling” towards Earth due to gravity, but its horizontal velocity keeps it in orbit instead of crashing into Earth.
