This note covers all chapters in the new
Physics 9702 Syllabus. The new chapter,
Astronomy, is also included. For every
subtopic, there are the syllabus content,
terms and definition, key points and
explanations of the concepts,formula
derivation and some spot question from
actual CIE exam.
12.1 Kinematics of uniform circular motion
● define the radian and express angular displacement in radians
● understand and use the concept of angular speed
TERMS DEFINITION/ FORMULA
Angular - Change in angle of a body
displacement - as it rotates around a circle
Radian - Angle subtended at the centre of a circle
- by an arc of length equal to the radius of the circle
Angular velocity - Rate of change of angular displacement
- swept out by radius
Angular speed 1. string:
- Rate of change of angle
- by the string
2. ball :
- Change in angular displacement
- per unit time
● Relationship between v, r and ω
- ω : angular velocity / angular frequency
1
,12.2 Centripetal acceleration
1. understand that a force of constant magnitude that is always perpendicular to the
direction of motion causes centripetal acceleration
2. understand that centripetal acceleration causes circular motion with a constant
angular speed recall and use a = rω2 and a = v2 / r
3. recall and use F = mrω2 and F = mv2 / r
4. recall and use ω = 2π / T and v = rω
TERMS DEFINITION/ FORMULA
Centripetal force - Force that is always directed towards the centre of the
circle
- and at right angles to the velocity of the body
Centripetal - Acceleration that is always directed towards the centre of
acceleration the circle
Revolution - A type of circular motion where the object moves around a
fixed centre point called the axis of revolution
● Effects of centripetal force :
- The force can indeed accelerate the object
- by changing its direction, but it cannot change its speed
- direction of the acceleration is inwards
● Centripetal force vs Centrifugal force
Centripetal force Centrifugal force
Force required for circular motion Force that makes something flee from the
centre
Toward the centre Away from the centre
2
,● Derivation of formulae
∆𝑣 𝑣∆𝑠
𝑎 = ∆𝑡
= 𝑟∆𝑡
∆𝑠 = 𝑎𝑟𝑐 𝑙𝑒𝑛𝑔𝑡ℎ = 𝑟∆θ
∆θ
𝑎 = 𝑣 ∆𝑡
= 𝑣ω
𝑎 =𝑣ω
𝑣 = ω𝑟
2
𝑎=ω 𝑟
𝐹 = 𝑚𝑎
2
𝑎=ω 𝑟
2
𝐹 = 𝑚ω 𝑟
2π
ω= 𝑇
ω = 2π𝑓
3
, CHAPTER 13 : GRAVITATIONAL FIELDS
13.1 Gravitational field
● understand that a gravitational field is an example of a field of force and define
gravitational field as force per unit mass
● represent a gravitational field by means of field line
TERMS DEFINITION/ FORMULA
Gravitational fields - Region of space of are/volume
- where a mass experiences gravitational force
Gravitational field strength - Force per unit mass
● Gravitational field lines
- Direction of gravitational field : radially inwards
- Lines of equal field strength
- uniform gravitational field (i.e on Earth’s surface)
- parallel field lines
13.2 Gravitational force between point masses
● understand that, for a point outside a uniform sphere, the mass of the sphere
may be considered to be a point mass at its centre
● recall and use Newton’s law of gravitation F = Gm1m2 / r2 for the force between
two point masses
● analyse circular orbits in gravitational fields by relating the gravitational force to
the centripetal acceleration it causes
● understand that a satellite in a geostationary orbit remains at the same point
above the Earth’s surface, with an orbital period of 24 hours, orbiting from west to
east, directly above the Equator
4
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