AQA Physics Unofficial Mark Scheme.

Physics unit 3 unofficial mark scheme 2015.

Pendulum

Focal length (2 marks)
p = 1/f
p = 1/0.8
p = 1.25 dioptres

Two conclusions can be made from the table? (2 marks)

-As length of wire increases, so does oscillations.
-As mass increases, there's no change to oscillations.

How can she improve the validity of her conclusions (2 marks)
-Repeated readings, calculating a mean.
-Acquiring results from other people, making results reproducible.

Units for formal length (1 mark)Metres, or M.

Eye

Labeling (2 marks)

-Suspensory ligaments
-Retina

Function of iris (1 mark)

Muscle contracts or relaxes, controlling amount of light entering pupil.

Defect&how to correct (2 marks)

Short sighted and diverging lens.

Diverging graph (3 marks)

Why is it important for the power of the lens be adjusted? (1 mark)

They allow the eye to focus on objects both far away and close, ie changing the power of the lens.

Power graph

From the age 10-30 and 50-70, what happens to power of lens? (3 marks)

There was a greater decrease between 50-70 it was 3.3 and from 10-30 it was 2.7.

Estimation of a 90 year old woman (1 mark)

0.8 Dioptres

Ultrasound and x-rays

Two missing blanks (2 marks)

-20 000 minimum frequency
-Diameter of an atom.

6 mark question on comparative reasons, uses, risks and precautions.

X-rays

-Used in x-rays and CT Scanner
-Absorbed by bone to check for fractures.
-Are ionising so harmful to cells/tissues and could cause cancer. Hence why the person conducting would stand behind a screen.

Ultrasound

-Ultrasound is used for prenatal scanning and to break up kidney stones.
-Ultrasound is just a sound wave and has no risks compared to X-rays-which are ionising.
-Has a frequency higher than 20,000 hz.

Centripetal force and CM.


Which way? (1 mark)

D.

Force? (1 mark)

Friction.

Factors affecting? (2 marks)
-Mass
-Velocity.

Why is it hard for race car to topple over? (2 marks)
-Height of the car is small, therefore low cm and harder to topple over.
-Base of the car is large, so more stable.

Bus questionWhy does the bus topple over once it reaches a certain angle? (2 mark)

Topples over because the line of action from the cm is beyond the base.

Give two reasons why they test angles that wouldn't normally happen at normal occurrence (2 marks)

-The greater the angle the bus can stand the more stable it is.
-Testing all circumstances such as an event of a tornado or earthquake.

Motor effect

Why does the wire move when the switch is closed? (3 marks)

Permanent magnets would produce a magnetic field and when the switch closed that'll produce a magnetic field because current would be running through the wire, both interfere with each other exerting a force.

Direction of force? (1)

Downwards.

When a.c is used what's the motion of the wire? (2 marks)

Moves both directions, because a.c would produce an alternating magnetic field.

What's the effect called? (1 mark)Motor.

Hydraulics

Property for liquids (1 mark)
-Water is virtually incompressible.
Accept "Water can equally transmitted through the water?"

Working out force hydraulics (3 marks)
-Mark for rearranging equation, making force subject.
-Mark for applying knowledge that pressure is the same throughout the water, so knowing this you'd work out pressure from first piston.
-Mark for your answer.300000x0.28=84000N

Refraction, critical angle.

Finish the line for refraction in figure x (1 mark)

Moves away from normal, because it's coming from high density to low density so speeds up.

Critical angle (2 marks)

-Mark for correct use of equation Refractive index = 1/ sin c
=1.56

Transformers

How is voltage created in the secondary coil? (3 marks)

An alternating current in the primary coil produces a changing magnetic field in the iron core and hence in the secondary coil. This induces an alternating p.d across the ends of the secondary coil.

How many turns in secondary coil?(2 marks)

-Mark for correct equation.
-18 turns for answer.

Credits go to Tue and Gecko242 for their help in preparing the mark scheme.

If any mistakes, please do comment with a valid justification. Cheers.

As always rep this post and I'll be sure to make the mark schemes for module one for all three sciences.

Some of these questions did not exist on that paper

Some of these questions did not exist on that paper

Some of these questions did not exist on that paper