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Physics GCSE > Physics 3 > Flashcards

Physics 3 Flashcards

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0
Q

What is a moment?

A

The turning effect of a force.

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1
Q

How do you work out the size of a moment?

A

M=Fxd

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2
Q

What is the centre of mass?

A

The point of the object which the whole mass is concentrated.

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3
Q

Where is the centre of mass?

A

Directly below the point of suspension.

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4
Q

What will happen if the anticlockwise moment is equal to the clockwise moment?

A

The object won’t turn.

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5
Q

What makes an object more stable?

A

A wide base and a low centre of mass.

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6
Q

The time for one pendulum swing depends on…

A

it’s length.

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7
Q

Time period=

A

1/Frequency

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8
Q

Why are liquids used in hydraulics?

A

They are virtually incompressible and their volume and density stay the same.

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9
Q

Pressure=

A

Force/Cross-sectional Area

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10
Q

What are hydraulics used for?

A

To lift heavy objects using a small force.

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11
Q

What is velocity?

A

The speed and direction of an object.

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12
Q

What is centripetal force?

A

The force that keeps something moving in a circle.

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13
Q

Centripetal force depends on…

A

mass, speed and radius.

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14
Q

What is a magnetic field?

A

A region where magnetic materials and wires carrying currents experience a force acting on them.

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15
Q

What does a soft iron core do?

A

Increases the strength of the magnetic field.

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16
Q

Why are electromagnets useful?

A

Their magnetism can be switched off.

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17
Q

What is the motor effect?

A

The force experienced by a current-carrying wire in a magnetic field.

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18
Q

What speeds up an electric motor?

A

More current and a stronger magnetic field.

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19
Q

Which way does a current move?

A

Positive to negative.

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20
Q

How can the direction of a motor be reversed?

A

By swapping over the polarity of the direct current (DC) supply or by swapping the magnetic poles over.

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21
Q

What is electromagnetic induction?

A

The creation of a potential difference across a conductor which is experiencing a change in magnetic field.

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22
Q

Moving a magnet in a coil of wire induces a…

A

voltage.

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23
Q

What would happen if you move the magnet in the opposite direction (in a coil of wire)?

A

The potential difference/current will be reversed too.

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24
Q

What do transformers do?

A

Change the potential difference - on an alternating current only.

25
Q

What do step-up transformers do?

A

Increase the voltage.

26
Q

What do step-down transformers do?

A

Decrease the voltage.

27
Q

Vp/Vs =

A

np/ns

28
Q

Vs/Vp =

A

ns/np

29
Q

The formula for power supplied in a transformer is…

A

Power=Current x Potential Difference

30
Q

Where are switch mode transformers used?

A

In chargers and power supplies.

31
Q

Refractive index=

A

Sin(i)/Sin(r) or 1/Sin(C)

32
Q

What is refraction caused by?

A

The waves changing speed.

33
Q

What happens when a ray is refracted?

A

It bends towards the normal, then away from the normal.

34
Q

Why kind of waves are X-rays?

A

Transverse.

35
Q

X-rays are ________ metal and bone, and are ___________ by body tissues.

A

absorbed, transmitted.

36
Q

Why are X-rays dangerous to cells?

A

They are ionising.

37
Q

What sort of image is formed in a CT scan?

A

A 3D image.

38
Q

Where are images formed in the eye?

A

The retina.

39
Q

What controls the size of the pupil?

A

The iris.

40
Q

What do the ciliary muscles do?

A

Change the shape of the lens.

41
Q

What is the far point?

A

The furthest distance that the eye can focus comfortably.

42
Q

What is the near point?

A

The closest distance that the eye can focus comfortably.

43
Q

What is the image like when it forms on the retina?

A

Real and inverted.

44
Q

What kind of lenses do short sighted people have?

A

Diverging/concave.

45
Q

What kind of lenses do long sighted people have?

A

Converging/convex

46
Q

What happens when ultrasound enters the body?

A

The waves are partially reflected back when they reach a boundary between two media with different densities.

47
Q

What is the object like when it’s further than 2F?

A

Diminished, inverted, real and between 2F and F

48
Q

What is the object like at 2F?

A

Same size, inverted, real, 2F

49
Q

What is the nature of the image between 2F and F?

A

Magnified, inverted, real, further than 2F

50
Q

What is the nature of the image at F?

A

No image is formed because the emerging rays are parallel to the axis

51
Q

What is the nature of the image that is closer than F?

A

Magnified, upright, virtual, same side as the object

52
Q

Magnification=

A

Image height/object height

53
Q

What is the function of the cornea?

A

Refracts light as it enters the eye (by a fixed amount)

54
Q

What is the image produced by a camera like?

A

Diminished, inverted and real (the same as the eye)

55
Q

What part of the camera performs a similar role to the ciliary muscles?

A

Focusing screws

56
Q

What part of the eye performs a similar role to the photosensitive surface?

A

Retina

57
Q

True or false? The power of a converging lens is negative.

A

False, it is positive

58
Q

What is lens power measured in?

A

Dioptres

59
Q

What is total internal reflection?

A

Beyond a certain point, called the critical angle, all the waves reflect back into the glass and no refraction occurs.

Physics GCSE (2 decks)

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