Quick revision for O Level Physics (includes radioactivity)

O LEVEL PHYSICS REVISION NOTES O LEVEL PHYSICS REVISION PREFACE: This book is prepared for Physics revision of the O level syllabus. The topics are presented in a short but accurate manner for a quick revision. No pictures or diagrams are used in this book to reduce the size. Readers should make it a point to refer back to their textbook for their reference. It is hoped that the book achieves its aim of helping readers to grasp the key facts for their revision.

O LEVEL PHYSICS REVISION NOTES CONTENTS: 1. MEASUREMENTS 2. SPEED, VELOCITY & ACCELERATION 3. FORCES 4. MOMENTS - THE TURNING EFFECTS OF FORCES 5. WORK, ENERGY & POWER 6. THERMAL EXPANSION 7. MEASUREMENT OF TEMPEARATURE 8. MELTING, BOILING & EVAPORATION 9. HEAT TRANSFER 10. WAVES - BASIC WAVE PROPERTIES 11. LIGHT 12. SOUND 13. MAGNETISM 14. STATIC ELECTRICITY 15. ELECTRICITY 16. ELECTRICAL ENERGY 17. ELECTROMAGNETIC INDUCTION 18. RADIOACTIVITY

O LEVEL PHYSICS REVISION NOTES 1. MEASUREMENTS Key notes: 1. The S.I unit for length is metre (m); for mass is kilogram (kg) and for time is seconds (s). 2. When using a ruler, try to avoid parallex and end errors. 3. The ruler can be read up to 1 decimal place in cm, e.g. 4.3cm. 4. The jaws of the vernier callipers enable us to measure the interval or external diameter of an object accurately. 5. The vernier callipers can be read up to 2 decimal places in cm, e.g. 2.34cm. A ruler can be read up to only 1 decimal place in cm, e.g. 2.3cm. 6. When reading the vernier callipers, (e.g. 2.34cm) 2.3cm is read from the main scale. 0.04cm is read from the vernier scale. 7. A micrometer screw gauge may be used to measure lengths less than 4cm. For length of 1cm to 10cm, the vernier callipers may be used. To measure length greater than 10cm, a metre rule is suitable. 8. The mass of an object is the amount of matter it contains. 9. The mass of an object is constant. 10. The period of oscillation of a simple pendulum increases as its length increases, but is independent of the amplitude of the oscillation and the mass of its bob. 11. Units for density : kg/m ³ or g/cm ³ 12. 1 g/cm ³ = 1000 kg/m ³ Formulas:  The Simple Pendulum Frequency, f = one second / period = 1 / T  Density, ρ = mass / volume

O LEVEL PHYSICS REVISION NOTES 2. SPEED, VELOCITY & ACCELERATION Key notes: 1. A scalar quantity has only a magnitude while a vector quantity has both a magnitude and a direction. 2. Speed is distance moved per unit time. It is a scalar quantity. 3. Velocity is distance moved per unit time in a particular direction. It is a vector quantity. 4. Displacement is the distance moved from a fixed point in a particular direction. 5. In a displacement-time graph, gradient = velocity. 6. For a particle moving with a constant velocity away from the observer, the gradient is a positive constant. 7. For a particle moving with a constant velocity towards the observer, the gradient is a negative constant. 8. For a particle moving with an increasing velocity away from the observer, the gradient is increasing. 9. For a particle moving with a decreasing velocity and eventually coming to a stop, the gradient is decreasing and eventually becomes zero. 10. Acceleration, a = rate of change of velocity. 11. Without air resistance, all objects fall with the same acceleration when released from rest. 12. The velocity-time graph of an object released from rest and falling freely will show a constant increaseof velocity with time. 13. Due to air resistance, an object released from a height eventually reaches a constant velocity called the terminal velocity. Formulas:  Speed = distance moved / time taken v = d / t (m/s or km/h)  Average speed = total distance moved / total time taken  Velocity = distance moved in a particular direction / time taken

O LEVEL PHYSICS REVISION NOTES  Acceleration = change of velocity / time taken for the change = (final velocity - initial velocity) / time taken for the change a = (v - u) / t or v = u + at where a = final velocity u = initial velocity t = time taken a = acceleration  In a velocity-time graph, gradient = acceleration, and area under the graph = distance travelled. (1/2) x time (s) x velocity (m/s)  FREE FALL & ACCELERATION DUE TO GRAVITY a = v - u / t a - acceleration v - velocity u - released from rest ( u = 0) t - time

O LEVEL PHYSICS REVISION NOTES 3. FORCES Key notes: 1. A force may produce a change in the shape and size of an object. 2. Below the limit of proportionality, the extension of a spring is directly proportional to the force applied on it. 3. The unit for force is the newton (N). 4. In changing the motion of an object, a force can cause it to start moving, to accelerate or decelerate, to change its direction of motion. 5. NEWTON ’ S LAWS OF MOTION: a) Newton ’ s first law of motion states that an object a rest will remain at rest b) An object moving with a uniform velocity will continue to do so UNLESS a resultant or net force acts on it. 6. Inertia is the tendency for a body to resist any change to its motion (i.e. whether it is stationary or moving with a uniform velocity.) 7. The greater the mass, the larger the inertia. 8. Newton ’ s second law states that: The acceleration of an object is directly proportional to the force applied on it. 9. Friction is a force that opposes motion. Its direction is always opposite to the direction of motion. 10. Friction depends on the nature of the surfaces in contact, the force pressing the two surfaces together. 11. Friction does not depend on the surface area in contact. 12. Friction can be an advantage or a disadvantage. 13. The mass of an object is the amount of matter it contains. It is always constant and does not change when gravity changes. 14. The weight of an object is the force due to gravity acting on the object. 15. The weight of an object is not constant but depends on the gravitational attraction. Formulas:  Hooke ’ s law: F ∝ e

O LEVEL PHYSICS REVISION NOTES F = ke F - force k - F / e (spring constant) e - extension  Newton ’ s Second Law of Motion, F = ma force = mass x acceleration  weight = mass x acceleration due to gravity W = mg - measured in newtons (N)

O LEVEL PHYSICS REVISION NOTES 4. MOMENTS - THE TURNING EFFECTS OF FORCES Key notes 1. The moment of a force means the turning effect of a force. 2. The principle of moments states that for an object in equilibrium, the sum of all clockwise moments = the sum of all anticlockwise moments. 3. Levers use the principle of moments. 4. If the distance of the effort from the fulcrum is greater than the distance of the load from the fulcrum, then a small effort can be used to lift a heavy load. 5. The centre of gravity of an object is the point where its whole weight seems to act. 6. When an object is hung freely, its centre of gravity is located vertically below the point of support. 7. An object is in a stable equilibrium if its centre of gravity is raised when tilted and it returns to its initial position when released. 8. An object is in unstable equilibrium if its centre of gravity is lowered when the object is tilted and it topples over to a new position when released. 9. An object is in a neutral equilibrium if its centre of gravity is not raised or lowered when displaced. 10. The stability of an object increase if its centre of gravity is lower or its base area is increased Formulas:  Moment = F x d = force x perpendicular distance from the pivot to the force Units is Nm (newton metre)

O LEVEL PHYSICS REVISION NOTES 5. WORK, ENERGY & POWER Key notes: 1. Energy is the capacity to do work. It is measured in joules. 2. The principle of conservation of energy states that energy can neither be created nor destroyed but it can be changed from one form to another. 3. In a falling object, the potential energy is converted into kinetic energy. 4. When friction is not negligible, work has to be done against it. 5. The main sources of energy are: fossil fuels, hydroelectric schemes, solar energy, geothermal energy and w