This page contains the AQA AS Physics P1 Gravitational Fields Questions and kerboodle answers for revision and understanding.This page also contains the link to the notes and video for the revision of this topic.
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21.1 Gravitational field strength AQA A2 Physics P21 Gravitational Fields Kerboodle Answers : Page No. 339
1.Ans-aLine of force, path followed by an electric charge free to move in an electric field or a mass free to move in a gravitational field, or generally any appropriate test particle in a given force field. 2.Ans-a i an Object Of mass 3.5 kg in a gravitational field at a position where g 9.5 N kg-1 33 N ii an object of mass 100 kg in a gravitational field at a position where g 1.6 N kg-1 160 N b i an Object Of mass 2. S kg experiences a force of 40 N, 16 N kg-1 ii an object of mass 18 kg experiences a force. 4.0 N kg-121.2 Gravitational potential AQA A2 Physics P21 Gravitational Fields Kerboodle Answers: Page No. 342
1.Ans-a 235 J 2.Ans-a 2.0 MJkg-1 b i the gravitational potential at the highest point reached by the rocket, -61 MJkg-1 ii 2.2 x 109 J 3.Ans- a.i -250 J ii O. -200 J iii R. -200 J b i P to o. 50 J ii Q to R 0 4 figure 5 shows equipotentials at a spacing of 1.0 km near a planet. The point labelled X is on the —500 kJ kg-I equipotential. a Demonstrate that the potential gradient at X is 5.0J kg-1 m-1 b 5 N kg-1 c 25 MJ21.3 Newton’s law of gravitation AQA A2 Physics P21 Gravitational Fields Kerboodle Answers: Page No. 345
1 a 1.3 x 10-6 N b 5.4mm 2 a 780 N b 6.0 x 1024 kg 3 a 0.5 1011m from the Sun, 54 N b 0.24 N 4 16.6 N ii 0.2 N b 16.4 N towards the centre of the Earth21.4 Planetary fields AQA A2 Physics P21 Gravitational Fields Kerboodle Answers: Page No.350
1 a 7.35 x 1022 kg 2 a i its surface, 272 N kg-1 ii 5.9 x 10-3 Nkg-1 b 3 a 0.028 N kg-1 c 7.1 x 106 J 4. 2.8 MJ kg-1, 1410 MJ21.5 Satellite motion AQA A2 Physics P21 Gravitational Fields Kerboodle Answers: Page No. 353
1 a r3/T2 = GM/4π2 Y is higher as longer time period means the orbit has a greater radius b Because the satellites are in geosynchronous orbit about 22,500 miles up. They appear to be standing still. They are orbiting the Earth but at the same speed as the Earth is rotating your satellite antenna has to be aligned so that it is pointing directly at the satellite you are receiving 2 a 3.4 x 106 m b 3.0 m s-2 c 5.2 x 1023 kg 3 a i M = mass of earth G = universal constant of gravitation m = mass of satellite r = radius of orbit The force and the acceleration are centripetal, and they both point from the position of the satellite toward the center of the earth. The gravitational force of the earth on the satellite is providing the centripetal force. GMm/r2 = mac ⇒ ac = GM/r2 ii Demonstrate that the speed of the satellite is given by the equation —gr, where g is the gravitational Field strength at the orbit. b i 9.5 N kg-1 ii 7.9kms-1 iii 5200 s 4 a Demonstrate that the speed v of a satellite in a circular orbit of radius r about a planet of magg M is given by the equation v? GM b A weather satellite is in a polar orbit above the Earth at a height of 1600 km. i Demonstrate that its speed is kms ii 7100 s Banner 4Practice questions: Page No. 354-357
1 a i (ii) b i Michell’s idea was put forward as a hypothesis because it was an untested idea, or a scientific hypothesis is a suggestion, prediction or untested idea. Einstein used mathematics to predict his General Theory of Relativity, ii Stars photographed near the Sun during a totalsolar eclipse were displaced relative to eachother. The light from each star was bent by the Sun’sgravitational field as it skimmed the Sun. This observation confirmed the prediction byEinstein. (c) Either- Scientific knowledge is expanded in scientific projects ✓, for example space exploration hasvastly increased our knowledge of the Solar System ✓
- New scientific projects can lead to important new discoveries ✓, for example HST led to the discovery of many stars and galaxies ✓
- Improved living conditions in poorer countries would benefit many more people than a space project would ✓, for example provision of clean water ✓
- Cost of the project would be met by taxpayers ✓ and there would be no direct immediate benefits ✓
- Improved living conditions in poorer countries would benefit many more people than a space project would – satellite communication has brought benefits to everyone, for example immediate disaster relief.
- Cost of the project would be met by taxpayers – more people would be employed as scientific firms would be contracted to supply parts.
- Scientific expertise could be better used – the demand for scientific expertise could be met by training more scientists If AGAINST:
- Scientific knowledge is expanded in scientific projects – there may be cheaper and less risky ways of pursuing knowledge of deep space (for example more advanced and bigger terrestrial telescopes linked to more powerful computers).
- New scientific projects can lead to important new discoveries – as above,
- Starts at 3R, with same initial value of g as existing curve;
- is a curve of decreasing negative gradient;
- shows the correct relationship, checked from points (for example at 6R, value should be exactly 1.0 vertical square; at 12R it should be 0.25 of a vertical square).
- It orbits over the Equator.
- It maintains a fixed position in relation to the surface of the Earth.
- It has a period of 24 hours (the same as the Earth’s period of rotation on its axis).
- The geosynchronous satellite enables uninterrupted communication between a transmitter and a receiver whereas the other satellite does not.
- Unlike the other satellite, the geosynchronous satellite does not require the use of a steerable dish.
- this force provides the centripetal force to keep the astronaut in orbit;
- the astronaut is in free fall, as is the spacecraft;
- the astronaut appears weightless because he or she is not supported.
- starts at distance = 1700 km
- ends at distance = 5700 km
- The satellite must be raised to a point beyond that at which the resultant gravitational field strength of the Earth/Moon is zero.
- This is much closer to the Moon than to the Earth.
- The Moon’s mass is much less than the Earth’s mass.
- The escape speed from the Moon is much less than that from Earth.
- On returning, the gravitational potential energy needed is much less so the kinetic energy at launch can be much less.
- The total rocket weight at launch is much greater on Earth.
- is proportional to the product of the masses
- and inversely proportional to the square of their separation.
- (i)
- Some of the rocket’s kinetic energy is converted into thermal energy in heating the rocket and the atmosphere.