Light bounces off objects. This is a good thing because it means that you can see stuff. If light strikes a flat mirror it bounces off in a predictable way. In the diagram below you can see a beam of light, P (called the incident ray) striking a reflective surface and being reflected, Q (called …
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Category:Physics
One Moment Please…
For a beam to balance the turning effect (also called a moment) on the left hand side must be the same as the turning effect on the right hand side. Another way of saying this is that the combined forces trying to rotate the lever anti-clockwise must be the same as those trying to turn …
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Slip Sliding Away…
I was asked why ice is slippery and this simple question turns out to be rather more tricky than expected. The simple answer is that the slipperiness comes from a thin layer of liquid water molecules on the surface of the ice. Ice as a solid has a crystalline structure with very little movement possible …
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How Old Is The Earth…
4.54 billion years old (4.54 × 109 years old) Well, I am glad that is settled. I heard a fellow on YouTube deriding science by saying… “First they told us that the Earth was less than 10,000 years old, then it was hundreds of thousands of years old, then millions, now it is billions of years …
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Van De Graaff Generator…
If you rub a piece of amber (fossilised tree resin) it becomes electrically charged and can be made to attract small objects. The Ancient Greek name for amber is ἤλεκτρον (ēlektron) which is where we get the word electricity. There is a force of attraction between positively charged protons and negatively charged electrons called the electrostatic …
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Newton’s Third Law…
Every action has an equal and opposite reaction. Newton’s Third Law explains that forces exist in equal and opposite pairs. If a force acts on an object in one direction then an equal forces pushes back in the opposite direction. We have adapted our catapults so that they sit on plastic rollers. This reduces the …
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Dark Matter and Dark Energy…
a post by Dreamy One aspect of the Universe’s expansion was quite certain in the early 1990s. Gravity was bound to slow the expansion over time, whether it had enough energy density to halt its expansion and collapse or not enough energy density to ever stop expanding. Even while the slowing had not yet been …
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Putting It All In Perspective…
This amazing graphic takes you on a journey from the highest mountain on Earth to the deepest trench of the oceans. Enjoy it as you scroll down the page. The outer layer of the Earth (the crust) ranges from 5 and 70 km thick. The Mariana Trench is just under 11 km deep. A journey all the way …
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AC/DC…
Given my fondness for the band of the same name, it is strange that I have not used this title for a post before. AC/DC refers in this case to alternating and direct current. Mains electricity in the UK is 240 volt alternating current that switches polarity (flows the opposite way) 50 times a second …
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Resistance Is Useless…
Sometimes exam questions about circuits will use resistors instead of lamps. Lamps are just like resistors except that they glow white-hot whereas resistors do their resisting more discreetly. Solving problems with resistors instead of lamps uses all the same principles. Often they include ammeters to show the current flowing in a particular part of the circuit and ask …
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