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What is homeostasis and why is it important? Give an example of a body condition that must be controlled and how.

In order to remember the definition of homeostasis it is useful to memorise the mnemonic ‘MACIE’; the Maintenance of A Constant Internal Environment. Conditions in the body must be constantly controlled beca...
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Answered by Tierney A. • Biology tutor
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Why can graphite conduct electricity but not diamond?

In graphite, each carbon atom is covalently bonded to three other carbon atoms. One of the four outer shell electrons of each carbon atom is therefore not engaged in bonding, and becomes delocalised. These d...
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Answered by Tierney A. • Chemistry tutor
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A wire has length l, cross-sectional area a, resistivity p and resistance R. It is compressed to a third of its original length but its volume and resistivity are constant. Show its new resistance is R/9.

First realize if its length is now l/3 but its volume is constant its cross sectional area is 3a. Substitute those into the equation for resistance R=p(l/a) and you get (1/9)(p(l/a))= R/9
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Describe how the strong nuclear force between two nucleons varies the distance between the 2 nucleons.

The strong force between two nucleons is initially repulsive. However at a distance of around 1 fm the force crosses over and becomes repulsive. The strong nuclear force is only seen to act over short distan...
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Two cars start at point A. Car 1 moves in a direction at 5 m/s. After 10 seconds car 2 accelerates in the same direction as car 1 at 2m/s^2. At what time after car 1 starts moving and distance from A does car 2 pass car 1?

-First find an equation for the distance travel by car 1. In this case s=5t+50 -Next find an equation for the distance traveled by car 2. Using suvat since constant acceleration (1/2)at^2+ut=s. Substitute kn...
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