In Sun-Earth system, the Sun, the Earth and the Lagrange point L4 form :
- A.an isosceles triangle
- B.an equilateral triangle
- C.a straight line
- D.a scalene triangle
Correct answer
Explanation
The correct answer is B, an equilateral triangle. L4 lies on Earth's orbit 60° ahead of the Earth, so it is as far from the Sun as from the Earth.
Lagrange points are five positions where a small object can stay in step with two large bodies because their gravity balances the motion. In the Sun-Earth system L1, L2 and L3 lie on the straight line through the Sun and the Earth: L1 between them, where India's Aditya-L1 observes the Sun, L2 beyond the Earth, where the James Webb Space Telescope sits, and L3 on the far side of the Sun. L4 and L5 sit 60° ahead of and behind the Earth on its orbit, each forming an equilateral triangle with the Sun and the Earth. Unlike L1 to L3, these two points are stable.
A is too loose: an equilateral triangle is a special isosceles one, but the accurate answer is equilateral. C, a straight line, describes L1, L2 and L3. D, a scalene triangle, would need three unequal sides, which is not the case.
Exam tip: L1, L2, L3 lie on the Sun-Earth line; L4 and L5 form equilateral triangles and are stable.
Practice Questions
View allWith reference to polyethylene terephthalate, the use of which is so widespread in our daily lives, consider the following statements :
1. Its fibres can be blended with wool and cotton fibres to reinforce their properties.
2. Containers made of it can be used to store any alcoholic beverage.
3. Bottles made of it can be recycled into other products.
4. Articles made of it can be easily disposed of by incineration without causing greenhouse gas emissions.
Which of the statements given above are correct?
- A.1 and 3
- B.2 and 4
- C.1 and 4
- D.2 and 3
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PET fibre (polyester) is blended with wool and cotton, and PET bottles are widely recycled into new products. Polyethylene terephthalate is a polyester made from ethylene glycol and terephthalic acid.
Read the full explanation →Consider the following pairs :
Objects in space : Description
1. Cepheids : Giant clouds of dust and gas in space
2. Nebulae : Stars which brighten and dim periodically
3. Pulsars : Neutron stars that are formed when massive stars run out of fuel and collapse
How many of the above pairs are correctly matched?
- A.Only one
- B.Only two
- C.All three
- D.None
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Only pair 3 is right; the descriptions of Cepheids and nebulae have been swapped. Cepheid variables are pulsating stars that brighten and dim on a regular cycle.
Read the full explanation →The terms 'Event Horizon', 'Singularity', 'String Theory' and 'Standard Model' are sometimes seen in the news in the context of
- A.Observation and understanding of the Universe
- B.Study of the solar and the lunar eclipses
- C.Placing satellites in the orbit of the Earth
- D.Origin and evolution of living organisms on the Earth
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All four terms come from physics and cosmology, the study of how the universe and its matter work. An event horizon is the boundary around a black hole beyond which nothing, not even light, can escape.
Read the full explanation →A charged particle moves through a magnetic field B with a velocity v. Which one of the following statements is true for the force (F) experienced by the particle?
- A.F is maximum when v and B are parallel to each other.
- B.F is maximum when v and B are anti-parallel to each other.
- C.F is maximum when v and B are perpendicular to each other.
- D.The force F is independent of the angle between v and B.
Show answer
The magnetic force depends on the sine of the angle between velocity and field, and sin 90° is the largest value.
Read the full explanation →Which one of the following is the most characteristic property of an element?
- A.Density
- B.Boiling point
- C.Mass number
- D.Atomic number
Show answer
The number of protons in the nucleus defines an element, and no two elements share it. The atomic number (Z) is the number of protons in an atom's nucleus, and in a neutral atom it also equals the number of electrons, which decide chemical behaviour.
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