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Two identical uniform spheres each of radius R are placed in contact. The gravitational force between them is F. They are then separated until the force between them is one ninth of the magnitude. What is the distance between the surfaces of the spheres?

With electostatics, it is important to remember that inthe equation giving the force between two point charges, the force is inversely proportional to the square of the distance of the charges. It is importa...
MS
Answered by Mrinank S. • Physics tutor
23856 Views

(2x + 3y)^2 – (2x – 3y)^2 = 360 show that xy is a multiple of 5

Expand first brackets: 4x 2 +6xy+6xy+9y 2 Expand second brackets: 4xy 2 -6xy-6xy+9y 2 Subtract the second expansion from the first one, being careful of the double negative: =24xy Then, back into the origina...
RM
Answered by Ryan M. • Maths tutor
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Where is DNA found in a human cell? What is a gene?

DNA is a long molecule found in the nucleus (or more specifically the nucleolus) of a human cell. When it is condensed and shortened it appears, under a microscope, as 23 pairs of chromosomes. A gene is a lo...
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Answered by Ryan M. • Biology tutor
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How do I analyse a text to A or A* level?

The examiners are looking for two things from your analysis of a text. Firstly, they want to know that you can identify literary techniques when they are used by the author. Literary techniques dont have to ...
RL
Answered by Ramganesh L. • English tutor
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Solve the simultaneous equations 5x + 3y = 24 and 3x - 4y = 26

Ok, so here are the equations5x+3y=243x-4y=26So let's multiply the first equation by 3, which gives us:15x+9y=72Now let's multiply the second equation by 5, which gives us:15x-20y=130So we're now left with:1...
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Answered by William S. • Maths tutor
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