Gravitational Field — Structured Questions (Cambridge International A-Level Physics): Exam Questions

Planets create large gravitational fields.

State what is meant by a gravitational field.

The Earth has a larger gravitational field strength than the moon.

State what is meant by gravitational field strength.

Saturn has a gravitational field strength of 10.5 N kg^–1 on its surface and a radius of 58 000 km.

(i) State the acceleration due to gravity of an object on Saturn.

(ii) Calculate the mass of Saturn.

Fig 1.1 represents Saturn as an isolated uniform sphere.

Sketch the lines to represent the gravitational field outside the sphere.

Astronaut A travels from the Earth to the Moon.

Explain the effect on astronaut A's mass and weight.

Determine the gravitational field strength of the Moon using the following information about the astronaut.

• $F_{gEarth}=770N$
• $F_{gMoon}=128N$

Astronaut A leaves the moon and visits the planet Mars. As they leave Mars, they notice that it takes less fuel to leave Mars' atmosphere than Earth's, but more fuel to leave Mars' atmosphere than the Moon's.

Suggest what this implies about the gravitational field strength on Mars.

Sketch a diagram of the gravitational field lines at the surface of Mars.

Sketch a diagram of the Earth's gravitational field:

i) At the surface.

ii) As a sphere.

Extract:

Sketch a diagram of the Earth's gravitational field: i) At the surface.

The Earth's gravitational field at the surface: At least 3 parallel field lines equally spaced; Field lines arrows pointing toward the surface of the Earth.

The planet Lamentis has a gravitational field strength twice that of Earth.

Sketch a diagram of the gravitational field at the surface of Lamentis.

Fig. 1.1 shows a small horizontal region on the surface of the Earth. X is a point underneath the surface which contains material of higher density than the material surrounding it.

On Fig. 1.1, draw the gravitational field lines on the surface of the Earth.

Fig. 1.1

The spacecraft Centurion leaves Earth for Venus to identify potential mining locations based on fluctuations in the gravitational field strength on the surface of Venus.

The Centurion sends a landing party to the surface in a shuttle. The shuttle has a mass of 3.24×10⁷ kg when launched from the Centurion, but loses 5% of its total mass in fuel combustion due to landing. The shuttle has a weight of 270 MN when it comes to rest on the surface of Venus.

Calculate the gravitational field strength on the surface of Venus.

Extract:

The spacecraft Centurion leaves Earth for Venus to identify potential mining locations based on fluctuations in the gravitational field strength on the surface of Venus. The Centurion sends a landing party to the surface in a shuttle. The shuttle has a mass of 3.24×10^7 kg when launched from the Centurion, but loses 5% of its total mass in fuel combustion due to landing. The shuttle has a weight of 270 MN when it comes to rest on the surface of Venus.

The landing crew collect rock samples from the landing site. When the landing crew has finished its mission, the shuttle launches to return to the Centurion. At an altitude of 250 km above the surface of Venus, the mass lost through fuel combustion is equal to the total mass of the rocks collected at the surface.

Gravitational force is inversely proportional to the square of the distance between masses.

$F\propto\frac{1}{r^{2}}$

Calculate the gravitational field strength of Venus at 250 km above the surface.

The radius of Venus is 6.3 × 10⁶ m.

An equation to describe field strength is:

$\mathrm{gravitational} \mathrm{field} \mathrm{strength}=\frac{X}{Y}$

Define X and Y in the equation above.

Extract:

An equation to describe field strength is: gravitational field strength = X/Y. Define X and Y in the equation above. X is: Force acting on an object with mass; Y is: Mass of object;

Based on your answer to part (a), define the terms in the following equation:

$g=\frac{F}{m}$

The following text is about gravitational fields.

Complete the following sentences by crossing out the incorrect words:

A gravitational field is a region of space in which objects with mass / charge will experience a force.

The direction of the gravitational field is always directed away from / towards the centre of the mass.

Gravitational forces are always / never attractive.

Gravitational fields around a point mass are uniform / radial.