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Topic 1 – Motion

Topic 1 – Motion. Vectors and scalars Distance/time graphs Acceleration Velocity/time graphs. Vectors and Scalars. Scalars – Magnitude (size) Vectors – Magnitude and direction. Distance-time graphs. Acceleration. Tells us how quickly velocity is changing each second.

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Topic 1 – Motion

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  1. Topic 1 – Motion • Vectors and scalars • Distance/time graphs • Acceleration • Velocity/time graphs

  2. Vectors and Scalars Scalars – Magnitude (size) Vectors – Magnitude and direction

  3. Distance-time graphs

  4. Acceleration Tells us how quickly velocity is changing each second. Units = m/s2 g = 10 m/s2

  5. Velocity-time graphs D C E B F A G H

  6. Velocity-time graphs To find the distance travelled, we must calculate the area under the graph.

  7. Exam Practise • Complete question 4 from your exam paper. • You have 11 minutes.

  8. Topic 2 – Forces and Motion • Resultant forces • Newton’s first law • Mass and weight • Newton’s second law • Newton’s thirds law • Momentum (higher tier only) • Stopping distances • Crash hazards

  9. To find the resultant force, you must add the forces if they act in the same direction, or subtract them if they’re in the opposite direction. Forces... • ...always act in action-reaction pairs. • When two objects meet they interact, each causing a force on the other. Action Reaction Free-body diagram

  10. Newton’s first law An object will stay in its state of rest or uniform motion unless made to change by a force acting on it. stay still keep moving ata constant speed

  11. Terminal Velocity Remember: • Weight pulls the object down; • Weight stays the same all the way down. • Air resistance increases as the object falls; • It NEVER gets bigger than weight; • When the forces are balanced, the object is at terminal velocity so will travel an equal distance in equal time.

  12. Newton’s second law An object will be able to accelerate faster if it has a small mass and a big force acting on it. Inertia – the more massive an object, the more force you need to apply to make it move. HIGHER ONLY

  13. Investigating acceleration The ramp is tilted to account for friction – you should tilt it until the trolley just starts moving.

  14. Newton’s third law Every action has an equal and opposite reaction. • Action-reaction forces act on different objects. • Balanced forces act on the same object.

  15. Momentum HIGHER ONLY Which would be harder to stop? • A large heavy ball or a small light one? • A fast ball or a slow on of the same mass? How hard an object is to stop is known as it’s momentum and it depends on it’s velocity and mass. Momentum = mass x velocity

  16. Momentum is always conserved. HIGHER ONLY The total momentum of two objects before they collide is equal to the total momentum after the collision. p1 + p2 = ptotal 300kgms-1 100kgms-1 200kgms-1

  17. Stopping Distance Thinking distance is the distance a car travels before the brakes are applied. Braking distance is the distance a car travels whilst the brakes are being applied. Alcohol, drugs, loud music, mobile phones, distractions. Weather, condition of the brakes, road surface.

  18. Car Safety How many car safety features can you list? How do these work? If we increase the time for an impact to happen then we can decrease the force applied to an object during that collision.

  19. Exam Practise • Complete question 6 from your exam paper. • You have 12 minutes.

  20. Topic 3 – Energy • Conservation of energy • Energy efficiency • Keeping warm • Non-renewable energy • Renewable energy

  21. Energy Transfers Law of conservation of energy: Energy is never created or destroyed, only transferred to other forms or the surroundings. Types of Energy: • Chemical • Elastic Potential • Electrical • Gravitational Potential • Kinetic • Light • Nuclear • Sound • Thermal

  22. Sankey Diagrams These show energy conservation, the width of the arrows represents the amount of energy in joules.

  23. Efficiency Calculation How good a device is at converting energy into useful forms is know as its efficiency.

  24. Keeping Warm Energy can be transferred by heating via: • Conduction • Convection • Radiation We can use insulation to reduce heat transfer. Gas is the best insulator. Why might this be?

  25. GPE and KE When an object is off the ground it has gravitational potential energy. GPE = mgh When an object is moving it has kinetic energy. KE = ½ mv2 Energy is conserved. This means that however much energy we have at the start, we will have at the end. It will be transferred to different forms along the way.

  26. Non-Renewable Resources

  27. Renewable Resources

  28. Exam Practise • Complete question 6c from your exam paper. • You have 6 minutes.

  29. Topic 4 – Waves • Describing waves • Wave speeds • Refraction • Waves crossing boundaries* • Ears and hearing* • Ultrasound* • Infrasound* * = triple only

  30. Waves Transfer Energy TRANSVERSE: Move at right angles to the vibration (Up and Down) LONGITUDINAL: Move in the same direction as the vibration (Left and Right)

  31. Waves FREQUENCY: The number of waves that pass a point in a second PERIOD: Time taken for one complete wave to pass.

  32. Wave Equations WAVE SPEED = FREQUENCY X WAVELENGTH (m/s) (Hz) (m) WAVE SPEED = DISTANCE / TIME (m/s) (m) (s)

  33. Refraction Light travels in straight lines. When it enters another material it bends at an interface (boundary). A line at 90o to the interface is called the normal. Changes speed and direction.

  34. HIGHER ONLY Refraction • Wavefronts show wave peaks. • Frequency stays the same but the wavelength changes because the speed changes.

  35. TRIPLE ONLY Waves crossing boundaries • Reflected • Refracted • Transmitted – wave passes through material. • Absorbed – wave ‘disappears’ as energy is transferred to the material.

  36. TRIPLE ONLY HIGHER ONLY Ears and hearing Sound waves cause changes in pressure on the surface of a solid.

  37. TRIPLE ONLY HIGHER ONLY Ears and hearing The cochlea is a coiled tube containing liquid. It can detect different frequencies of sound from 20 to 20000 Hz.

  38. Ultrasound Sounds above 20000 Hz.

  39. Ultrasound

  40. Infrasound TRIPLE ONLY HIGHER ONLY • Any sound below 20Hz is known as Infrasound. • Infrasound is very useful as it travels very long distances and can be used as a method of communication between animals and a way of detecting Earthquakes and Volcanoes.

  41. TRIPLE ONLY HIGHER ONLY Infrasound Tell us about the Earth’s structure. • Primary waves (longitudinal) • Secondary waves (transverse)

  42. Exam Practise • Complete question 2 from your exam paper. • You have 9 minutes.

  43. Topic 5 – Light and the EM Spectrum • Ray diagrams* • Colour* • Lenses* • The EM spectrum • Uses and dangers of EM waves • Radiation and temperature* * = triple only

  44. TRIPLE ONLY Reflection angle of incidence = angle of reflection

  45. TRIPLE ONLY Total internal reflection Rather than passing through the glass block and being refracted, the light is reflected. The angle of incidence must exceed the critical angle.

  46. TRIPLE ONLY Colour

  47. TRIPLE ONLY Colour

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