Physics 3

Question 0

What is a moment?

Answer 0

The turning effect of a force.

Question 1

How do you work out the size of a moment?

Answer 1

M=Fxd

Question 2

What is the centre of mass?

Answer 2

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

Question 3

Where is the centre of mass?

Answer 3

Directly below the point of suspension.

Question 4

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

Answer 4

The object won’t turn.

Question 5

What makes an object more stable?

Answer 5

A wide base and a low centre of mass.

Question 6

The time for one pendulum swing depends on…

Answer 6

it’s length.

Question 7

Time period=

Answer 7

1/Frequency

Question 8

Why are liquids used in hydraulics?

Answer 8

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

Question 9

Pressure=

Answer 9

Force/Cross-sectional Area

Question 10

What are hydraulics used for?

Answer 10

To lift heavy objects using a small force.

Question 11

What is velocity?

Answer 11

The speed and direction of an object.

Question 12

What is centripetal force?

Answer 12

The force that keeps something moving in a circle.

Question 13

Centripetal force depends on…

Answer 13

mass, speed and radius.

Question 14

What is a magnetic field?

Answer 14

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

Question 15

What does a soft iron core do?

Answer 15

Increases the strength of the magnetic field.

Question 16

Why are electromagnets useful?

Answer 16

Their magnetism can be switched off.

Question 17

What is the motor effect?

Answer 17

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

Question 18

What speeds up an electric motor?

Answer 18

More current and a stronger magnetic field.

Question 19

Which way does a current move?

Answer 19

Positive to negative.

Question 20

How can the direction of a motor be reversed?

Answer 20

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

Question 21

What is electromagnetic induction?

Answer 21

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

Question 22

Moving a magnet in a coil of wire induces a…

Answer 22

voltage.

Question 23

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

Answer 23

The potential difference/current will be reversed too.

Question 24

What do transformers do?

Answer 24

Change the potential difference - on an alternating current only.

Question 25

What do step-up transformers do?

Answer 25

Increase the voltage.

Question 26

What do step-down transformers do?

Answer 26

Decrease the voltage.

Question 27

Vp/Vs =

Answer 27

np/ns

Question 28

Vs/Vp =

Answer 28

ns/np

Question 29

The formula for power supplied in a transformer is...

Answer 29

Power=Current x Potential Difference

Question 30

Where are switch mode transformers used?

Answer 30

In chargers and power supplies.

Question 31

Refractive index=

Answer 31

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

Question 32

What is refraction caused by?

Answer 32

The waves changing speed.

Question 33

What happens when a ray is refracted?

Answer 33

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

Question 34

Why kind of waves are X-rays?

Answer 34

Transverse.

Question 35

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

Answer 35

absorbed, transmitted.

Question 36

Why are X-rays dangerous to cells?

Answer 36

They are ionising.

Question 37

What sort of image is formed in a CT scan?

Answer 37

A 3D image.

Question 38

Where are images formed in the eye?

Answer 38

The retina.

Question 39

What controls the size of the pupil?

Answer 39

The iris.

Question 40

What do the ciliary muscles do?

Answer 40

Change the shape of the lens.

Question 41

What is the far point?

Answer 41

The furthest distance that the eye can focus comfortably.

Question 42

What is the near point?

Answer 42

The closest distance that the eye can focus comfortably.

Question 43

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

Answer 43

Real and inverted.

Question 44

What kind of lenses do short sighted people have?

Answer 44

Diverging/concave.

Question 45

What kind of lenses do long sighted people have?

Answer 45

Converging/convex

Question 46

What happens when ultrasound enters the body?

Answer 46

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

Question 47

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

Answer 47

Diminished, inverted, real and between 2F and F

Question 48

What is the object like at 2F?

Answer 48

Same size, inverted, real, 2F

Question 49

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

Answer 49

Magnified, inverted, real, further than 2F

Question 50

What is the nature of the image at F?

Answer 50

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

Question 51

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

Answer 51

Magnified, upright, virtual, same side as the object

Question 52

Magnification=

Answer 52

Image height/object height

Question 53

What is the function of the cornea?

Answer 53

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

Question 54

What is the image produced by a camera like?

Answer 54

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

Question 55

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

Answer 55

Focusing screws

Question 56

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

Answer 56

Retina

Question 57

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

Answer 57

False, it is positive

Question 58

What is lens power measured in?

Answer 58

Dioptres

Question 59

What is total internal reflection?

Answer 59

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