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Two bodies of masses $M$ and $m$ are separated by a distance $r$. According to Newton's law of gravitation, what is the nature of the force between them?

  • The force can be either attractive or repulsive depending on the medium between the bodies.
  • The force is always repulsive, pushing the bodies away from each other.
  • The force is attractive, pulling the bodies towards each other. (correct)
  • There is no force between the bodies as long as they are stationary.

Two objects with masses $M$ and $m$ interact gravitationally. Which factor, when increased, would decrease the gravitational force between them?

  • The sum of the masses ($M + m$).
  • The product of the masses ($M \times m$).
  • The gravitational constant.
  • The distance ($r$) separating their centers. (correct)

If the distance between two bodies is doubled, what happens to the gravitational force between them?

  • It becomes four times the original force.
  • It reduces to one-quarter of the original force. (correct)
  • It doubles.
  • It remains the same.

Consider two objects interacting gravitationally. If the mass of one object is doubled while the distance between them is also doubled, how does the gravitational force change?

<p>It is halved. (A)</p> Signup and view all the answers

Two spheres of masses $m_1$ and $m_2$ are placed a distance $r$ apart. If $m_1$ is increased to $4m_1$ and $r$ is increased to $2r$, what is the new gravitational force between them?

<p>The gravitational force will remain the same. (C)</p> Signup and view all the answers

Two celestial bodies are separated by a distance, $r$. If the distance between them is doubled, how does the gravitational force, $F$, between them change?

<p>F is reduced to $\frac{1}{4}$ of its original value. (D)</p> Signup and view all the answers

A hypothetical planet has a radius of $R$ and an acceleration due to gravity of $g$ at its surface. What is the escape velocity from this planet in terms of $R$ and $g$?

<p>$\sqrt{2gR}$ (C)</p> Signup and view all the answers

The mass of Earth is calculated using the formula derived from Newton's law of universal gravitation. If the measured radius of the Earth were smaller than the actual radius by a factor of two, how would this affect the calculated mass, assuming $g$ and $G$ are known and constant?

<p>The calculated mass would be four times smaller. (C)</p> Signup and view all the answers

Two spheres of masses $m_1$ and $m_2$ are separated by a distance $r$. If the mass of each sphere is doubled, what happens to the gravitational force between them?

<p>It is quadrupled. (B)</p> Signup and view all the answers

Consider two objects attracting each other gravitationally. If the gravitational constant, $G$, were suddenly doubled, while all other parameters (masses and distance) remained the same, what would happen to the gravitational force between them?

<p>It would double. (B)</p> Signup and view all the answers

How does the gravitational force (F) between two masses change if the distance (r) between their centers is doubled?

<p>F is quartered. (D)</p> Signup and view all the answers

A planet has a mass M and a radius R. If the acceleration due to gravity on the planet's surface is g, which formula correctly expresses the mass of the planet?

<p>$M = \frac{gR^2}{G}$ (D)</p> Signup and view all the answers

What happens to the escape velocity of a planet if both its mass and radius are doubled?

<p>The escape velocity increases by a factor of $\sqrt{2}$. (C)</p> Signup and view all the answers

According to Kepler's Law of Periods, how does the period (T) of a planet's orbit relate to its average distance (r) from the Sun?

<p>$T^2 \propto r^3$ (D)</p> Signup and view all the answers

A spacecraft is launched from Earth. Which of the following changes would decrease the escape velocity required for the spacecraft?

<p>Decreasing the universal gravitational constant (G). (A)</p> Signup and view all the answers

Planet X has a gravitational potential of V at its surface. What is the physical significance of the absolute value of the gravitational potential, |V|, in relation to escape velocity?

<p>The escape velocity is equal to $\sqrt{2|V|}$. (D)</p> Signup and view all the answers

A planet orbits a star in an elliptical path. According to Kepler's Law of Areas, where does the planet move the fastest in its orbit?

<p>When it is closest to the star. (B)</p> Signup and view all the answers

Two planets have the same radius, but Planet A has twice the mass of Planet B. How does the gravitational potential at the surface of Planet A compare to that of Planet B?

<p>Planet A has twice the gravitational potential of Planet B. (B)</p> Signup and view all the answers

Flashcards

Gravitational Interaction

Force existing between two bodies with masses M and m separated by a distance r.

Newton's Law of Gravitation

States that a force exists between interacting bodies.

Line of Action (Gravity)

The straight line joining the centers of two interacting masses.

Attractive Force (Gravity)

A force that causes objects to come together.

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Distance 'r' in Gravitation

The distance 'r' is measured from the center of one mass to the center of the other mass.

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Gravitational Force

The attractive force between two masses.

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Formula for Gravitational Force

F = GMm/r^2. F is force, G is the gravitational constant, M and m are masses, and r is the distance between masses.

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Gravitational Potential (V)

The gravitational potential energy per unit mass at a point in space.

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Formula for Gravitational Potential

V = -GM/r, where G is the gravitational constant, M is the mass, and r is the distance from the center of the mass.

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Planet's mass (M)

M = (gR^2)/G, where g is the acceleration due to gravity, R is the radius of the planet, and G is the gravitational constant.

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Escape Velocity (v)

The minimum speed needed for an object to escape the gravitational influence of a massive body.

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Formula for Escape Velocity

v = √(2GM/r), where G is the gravitational constant, M is the mass, and r is the radius.

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Kepler's Law of Orbits

Each planet orbits the Sun in an ellipse, with the Sun at one focus.

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Escape Velocity

The required velocity for an object to escape a planet's gravitational pull.

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Value of Gravitational Constant (G)

G = 6.67 × 10-11 Nm2kg-2

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Gravitational Force Calculation (Example)

F = 1.31 × 1022 N

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Escape Velocity Formula

v = √2𝑔𝑟

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Mass of the Earth (M)

M = 5.99 × 1024 kg

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Study Notes

  • If there are two bodies of masses M and m whose centers are separated by a distance r, they exert a force of interaction on each other, which can be attractive or repulsive.
  • This force acts along the common centers of the bodies

Newton's Law of Gravitation

  • Defines the force between two interacting bodies: F = G (Mm / r^2)
  • F is measured in Newtons (N)
  • The relationship F ∝ 1/r^2 is an inverse-square law
  • F represents the force between the interacting masses (in N)
  • r is the distance between the centers of the masses (in m)
  • G is the universal gravitational constant (G = 6.67 × 10^-11 Nm^2kg^-2)

Gravitational Potential (V)

  • Formula: V = -GM/r or V = -gr
  • Measured in Nmkg^-1
  • M is the mass of the planet in kg
  • r is the radius of the planet in m
  • g is the acceleration due to gravity on the planet in ms^-2

Mass M of a Planet

  • Can be calculated using: M = gR^2/G
  • Where all the parameters maintain their meanings

Escape Velocity (v)

  • Formula: v = √(2GM/r) or v = √(2gr) or v = √(2|V|)
  • |V| is the magnitude of the gravitational potential in Nmkg^-1
  • M is the mass of the planet in kg
  • r is the radius of the planet in m

Kepler's Laws of Planetary Motion

Law of Orbits

  • Each planet moves in an elliptical orbit with the Sun at one focus of the ellipse

Law of Areas

  • A line joining the Sun to a given planet sweeps out equal areas in equal times

Law of Periods

  • The squares of the periods of revolution of the planets are proportional to the cubes of their mean distances from the Sun

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