Untitled Deck

Question 1

What is a gravitational field?

Answer 1

A gravitational field is a region around a body that has mass, in which another body with mass experiences a force.

Question 2

What happens when a small mass is placed close to a massive body?

Answer 2

The small mass and the massive body attract each other with equal and opposite forces. The small mass is pulled towards the massive body, following a path called a field line.

Question 3

What is gravitational field strength?

Answer 3

Gravitational field strength is the force per unit mass on a small test mass placed in the field at that point.

Question 4

What are the units of gravitational field strength?

Answer 4

Gravitational field strength is a vector quantity with units N kg⁻¹.

Question 5

What do the field lines around a planet indicate?

Answer 5

The field lines are radial and point towards the center of the planet, indicating the strength of the field, which decreases with increasing distance from the body.

Question 6

What is the gravitational field strength of the Earth at its surface?

Answer 6

The gravitational field strength of the Earth at the surface is 9.8 N kg⁻¹.
The gravitational field strength, is the force per unit mass on a small test mass placed in
the field at that point.

Question 7

What is the weight of an object?

Answer 7

The weight of an object is the force of gravity acting on it.

Question 8

What is the acceleration due to gravity?

Answer 8

The acceleration due to gravity equals the gravitational field strength, g, and is measured in N kg⁻¹ or m s⁻².

Question 9

What does Newton’s Law of Gravitation state?

Answer 9

Any two point masses attract each other with a force that is proportional to each of their masses and inversely proportional to the square of the distance between them.

Question 10

What is the Universal Gravitational constant?

Answer 10

The Universal Gravitational constant, G, is 6.67 x 10⁻¹¹ N m² kg⁻¹.

Question 11

How does gravitational strength behave at a distance from a spherical mass?

Answer 11

The gravitational strength at a distance r from the center of a spherical mass is the same as if the mass were concentrated at its center, provided that r ≥ R.

Question 12

What is the variation of gravitational field strength with distance from a spherical planet?

Answer 12

At the surface of a spherical planet, the gravitational field strength is maximum and decreases with increasing distance from the center.

Question 13

What is the gravitational potential energy?

Answer 13

Gravitational potential energy is the energy of an object due to its position in a gravitational field.

Question 14

What is gravitational potential?

Answer 14

Gravitational potential at a point is the work done per unit mass in bringing the mass from infinity to that point.

Question 15

What is the gravitational potential at infinity?

Answer 15

The gravitational potential at infinity is defined as zero.

Question 16

What is escape speed?

Answer 16

Escape speed is the speed needed by an object to escape from the gravitational force of attraction of the Earth or other planet.

Question 17

What is the relationship between potential energy and kinetic energy for a satellite?

Answer 17

The total energy of a satellite in orbit is the sum of its potential and kinetic energies, with the total energy always being negative.

Question 18

How does gravitational potential vary with distance from the center of the Earth?

Answer 18

The gravitational potential decreases (becomes more negative) as the distance from the center of the Earth increases.

Question 19

What is the effect of Earth’s rotation on gravitational strength at the equator?

Answer 19

At the equator, a body experiences a centripetal acceleration due to Earth’s rotation, which reduces the effective gravitational strength.

Question 20

What is the gravitational field strength at the poles and equator?

Answer 20

g at the poles = 9.83 m s⁻²; g at the equator = 9.78 m s⁻².

Question 21

What is Kepler’s third law of planetary motion?

Answer 21

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