CIE A2 Physics (9702) full notes - StudyLast

CIE A2 Physics (9702)

Key: Blue These are derivations that might get too mathematical for some. It is for a more comprehensive understanding. Those who aren't really interested in knowing more can ignore. Red Very very important stuff from past years, they're basically marking schemes.

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Physics

Contents

1 Circular Motion

3

2 Gravitational Field

6

3 Oscillation

13

4 Ideal Gases

16

5 Temperature

19

6 Thermal Properties

21

7 Communication

23

8 Electric Fields

33

9 Capacitance

38

10 Electronics

47

11 Magnetic Fields and Electromagnetism

53

12 Electromagnetic Induction

59

13 Alternating Current

62

14 Nuclear Physics

68

15 Quantum Physics

71

16 Medical Physics

78

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1 Circular Motion

Concepts and Formulae Derivation

Centripetal force is the net force acted on an object towards its centre of rotation. The object is accelerating

due to this net force, but the speed of the object remains constant, the acceleration caused by the centripetal force

only affects the instantaneous direction of motion. We define the velocity of covering a certain angle by angular

velocity, .

=

t

To calculate centripetal force, we can use Newton's 2nd law, F = ma, the acceleration towards the centre, a, is

given by

v 2 a = = r2

r

It can be derived as follow

Derivation of centripetal acceleration. (Source: Physics Wiki)

v = v2 - v1

When 0, v 0 which means

v1 v2 = v = v v

This yields the following relation

v v v

AB

=

r

=

r

Since AB= vt, we can deduce the following equation

v v

v v 2

= = = = a

vt r

t r

We can also multiply the angular velocity, , by the velocity, v, to get the acceleration, a, this is because the change in angle causes the direction of velocity to change (the magnitude isn't changing, v here just means the direction of velocity is changing).

v v v = = = a

t t Therefore with acceleration figured out, we can find the centripetal force Fc using Newton's 2nd law

Fc

=

ma

=

v 2 m

r

=

mr2

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Horizontal Rotation

Vertical Rotation

T cos = mg v 2

T sin = Fc = m r = mr2

If the speed of the objects moving in the circle path is constant, then v 2

T1 = T2 - mg = T3 - mg cos = T4 + mg = T5 + mg cos = m r

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Vehicle on a Banked Road

N = mg cos

Fc

=

N

sin

=

v 2 m

r

Since weight of the car is constant, therefore Fc, is constant, as a result if the velocity of the vehicle, v, is increased, r, will so increase which implies that the car will move up the slope to increase the radius of circular

rotation so that the constant is not changed.

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