Stability is affected by the height of an object, the size of its base, and the position of the centre of mass (gravity) - where the weight seems to act.
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What is the place where the sea saw twists around called?
Pivot
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Define a MOMENT
A moment is the turning force about a pivot
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Why are CT scans better than basic X-rays?
CT scans produce a detailed 3D image of which shows both tissue and bone. Therefore they are better at diagnosing medical problems.
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What is refraction caused by?
Waves changing speed
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What is total internal reflection used in?
It's used in fibre optics, as the light ray stays inside the fibre due to TIR, also endoscopes which illuminate and see inside the body - goes round corners/flexible, aids keyhole surgery.
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What happens when light refracts?
It bends towards/away from the normal
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How does the eye produce an image?
It uses a convex lens
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What is the IRIS?
It is a coloured ring of muscle, it controls the size of the pupil
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What is the PUPIL?
It allows light into the eye
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What is the CORNEA?
It is transparent, and convex in shape, it starts to focus the light.
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What is the OPTIC NERVE?
It sends messages from retina to brain via the optic nerve.
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What is the RETINA?
It is a light sensitve cell that detects the image (light) and sends messages to the brain.
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What is the LENS?
It focuses the light into the retina.
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What is the function of the CILIARY MUSCLE & SUSPENSORY LIGAMENT?
Ciliary muscle and suspensory ligaments make the lens fatter or thinner to change its focus depending on where the object is.
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What lens is used to correct LONG sighted vision?
A convex (converging) lens adds focus, as these people can focus on objects fair away but not on close objects.
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What lens is used to correct SHORT sighted vision?
A diverging lens to spread out the light rays before the lens focuses the light. These people can focus on objects close up but not far away objects.
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What is a split ring commutator?
Its a conducting ring with a gap between two halves. Its a clever way of connecting the motor and reversing the direction of the current reverses the direction of the force.
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Why is a split ring commutator needed in an electric motor using a direct current?
It is used to ensure that the current flows in one direction through the coil.
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Give two ways the speed of the electric motor can be increased?
It can be increased by changing the strength of the magnet, also by changing the number of coils.
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Give two ways the direction of rotation of a simple electric motor can be reversed?
Change the direction of the current and/or change the direction of the magnetic field.
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What is electromagnetic induction?
Its moving a wire through a magnetic field will induce a potentail difference (current).
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Why is an IRON CORE used in a transformer?
It increases the strength of the moving magnetic field and channels the magnetic field to the secondary coil.
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What is the function of the SECONDARY coil in a transformer?
Moving electromagnetic field cuts the coil and induces a potential difference (current).
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Why does a.c. have to be used in a transformer?
To produce a moving (alternating) magnetic field.
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How can you make an electromagnet stronger?
By increasing the current/voltage, adding more coils or putting an iron core in the middle of the coil.
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What is the place where the sea saw twists around called?
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