Physics Gravity and Gravitation 1 — Questions and Answers
Question 1: According to Newton's Law of Universal Gravitation, the force between two objects is:
- Directly proportional to the square of the distance between them
- Directly proportional to the product of their masses and inversely proportional to the square of the distance (Correct answer)
- Inversely proportional to the product of their masses
- Independent of the distance between them
Correct answer: Directly proportional to the product of their masses and inversely proportional to the square of the distance
Newton's Law states F = Gm₁m₂/r², so force increases with mass product and decreases with the square of distance.
Question 2: If the distance between two objects doubles, the gravitational force between them:
- Doubles
- Quadruples
- Decreases to one-quarter of the original (Correct answer)
- Decreases to one-half of the original
Correct answer: Decreases to one-quarter of the original
Since F ∝ 1/r², doubling the distance gives F ∝ 1/(2r)² = 1/(4r²), reducing the force to one-quarter.
Question 3: The acceleration due to gravity at Earth's surface is approximately:
- 6.67 × 10⁻¹¹ m/s²
- 9.8 m/s² (Correct answer)
- 3.7 m/s²
- 11.2 m/s²
Correct answer: 9.8 m/s²
Earth's surface gravitational acceleration g ≈ 9.8 m/s², a fundamental constant used in weight and free-fall calculations.
Question 4: Which of the following best describes gravitational potential energy near Earth's surface?
- PE = mgh, increasing as height increases (Correct answer)
- PE = mgh, decreasing as height increases
- PE = ½mv², independent of height
- PE = Gm₁m₂/r, always positive
Correct answer: PE = mgh, increasing as height increases
Gravitational PE near Earth's surface is PE = mgh, which increases as an object is lifted to a greater height.
Question 5: Kepler's First Law states that planetary orbits are:
- Perfect circles centered on the Sun
- Ellipses with the Sun at one focus (Correct answer)
- Parabolas with the Sun at the center
- Hyperbolas with the Sun at one focus
Correct answer: Ellipses with the Sun at one focus
Kepler's First Law states that planets travel in elliptical orbits with the Sun located at one of the two foci.
Question 6: The weight of an object is best defined as:
- The same as its mass
- The gravitational force exerted on it (Correct answer)
- Constant regardless of location in space
- Measured in kilograms
Correct answer: The gravitational force exerted on it
Weight is the gravitational force acting on an object, W = mg, and it varies depending on the local gravitational field strength.
Question 7: The universal gravitational constant G has a value of approximately:
- 9.8 m/s²
- 6.67 × 10⁻¹¹ N·m²/kg² (Correct answer)
- 3.0 × 10⁸ m/s
- 6.02 × 10²³ mol⁻¹
Correct answer: 6.67 × 10⁻¹¹ N·m²/kg²
The universal gravitational constant G ≈ 6.67 × 10⁻¹¹ N·m²/kg², a fundamental constant in Newton's law of gravitation.
Physics Gravity and Gravitation 1
According to Newton's Law of Universal Gravitation, the force between two objects is: