Physics-Gravitational Feilds

State what is meant by the term escape velocity. (1)

(Minimum) Speed (given at the Earth's surface) that will allow an object to leave / escape the (Earth's) gravitational field (with no further energy input)

State two reasons why rockets launched from the Earth's surface do not need to achieve escape velocity to reach their orbit. (2)

(Not given all their KE at Earth's surface) energy continually added in flight / continuous thrust provided / can use fuel (continuously)

What is the Gravitational potential on the surface of the earth

-63MJ

Which one of the following gives a correct unit for(g^2/G) ? A N m−2 B N kg−1 C N m D N

A N m−2

A projectile moves in a gravitational field. Which one of the following is a correct statement for the gravitational force acting on the projectile? A The force is in the direction of the field. B The force is in the opposite direction to that of the field. C The force is at right angles to the field. D The force is at an angle between 0° and 90° to the field.

A The force is in the direction of the field.

What is a force field:?

A region in which a body experiences a force

Equipotentials show...

All points of equal potential in a field

When a charge moves between two points in an electric field, or a mass moves between two points in a gravitational field, energy may be transferred. Which one of the following statements is correct? A No energy is transferred when the movement is parallel to the direction of the field. B The energy transferred is independent of the path followed. C The energy transferred is independent of the start and finish points. D Energy is transferred when the movement is perpendicular to the field lines

B The energy transferred is independent of the path followed.

Which one of the following statements about gravitational potential is incorrect? A It is analogous to the electric potential at a point in an electric field. B It is equal to the gravitational potential energy of a mass of 1 kg. C It is a vector quantity. D The difference in gravitational potential between two points at different heights above the Earth depends on the position of the points.

C It is a vector quantity.

Which one of the following statements about gravitational potential is correct? A gravitational potential can have a positive value B the gravitational potential at the surface of the Earth is zero C the gravitational potential gradient at a point has the same numerical value as the gravitational field strength at that point D the unit of gravitational potential is N kg^-1

C the gravitational potential gradient at a point has the same numerical value as the

Which one of the following statements about gravitational fields is incorrect? A Moving a mass in the direction of the field lines reduces its potential energy. B A stronger field is represented by a greater density of field lines. C Moving a mass perpendicularly across the field lines does not alter its potential energy. D At a distance r from a mass the field strength is inversely proportional to r.

D At a distance r from a mass the field strength is inversely proportional to r.

Gravitational field strength is...

Force per unit mass at a point in a gravitational field

Escape velocity is when....

Kinetic energy=gravitational potential energy

Gravitational potential is...

Potential energy per unit mass

State Newton's law of gravitation. (3)

force of attraction between two point masses (or particles) (1) proportional to product of masses (1) inversely proportional to square of distance between them (1)

State two features of a geo-synchronous orbit. (2)

orbits (westwards) over Equator (1) maintains a fixed position relative to surface of Earth (1) period is 24 hrs (1 day) or same as for Earth's rotation (1) offers uninterrupted communication between transmitter and receiver (1) steerable dish not necessary (1)

Satellites in orbits nearer the Earth than geo-synchronous satellites may be used in the future to track road vehicles. State and explain one reason why geo-synchronous satellites would not be suitable for such a purpose

signal would be too weak at large distance (1) the signal spreads out more the further it travels (1)

Explain what is meant by the gravitational potential at a point in a gravitational field. (2)

work done/energy change (against the field) per unit mass (1) when moved from infinity to the point (1)