1 / 86

Space for Reflection

Space for Reflection. W Richards. P5a Satellites, Gravity and Circular Motion. The Earth’s Orbit. Ellipse. Gravity. Note that this force goes both ways – the Earth is attracted to us. Gravity is an attractive force that affects anything with mass:. Centripetal force and The Earth.

jasoncoleman
Download Presentation

Space for Reflection

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Space for Reflection W Richards

  2. P5a Satellites, Gravity and Circular Motion

  3. The Earth’s Orbit Ellipse

  4. Gravity Note that this force goes both ways – the Earth is attracted to us. Gravity is an attractive force that affects anything with mass:

  5. Centripetal force and The Earth Gravity (and the fact that the Earth is moving at high speeds) keeps the Earth in orbit. Notice that the orbit path is slightly elliptical

  6. Orbit times Mercury = 88 days Mercury Venus Mars = 687 days Earth Mars Pluto = 90,500 days Jupiter Saturn Uranus Neptune Pluto

  7. Satellites The word “satellite” can be used to describe anything that _____ something else. The moon is a _______ satellite of the Earth and we also have many ________ satellites. All of these satellites are continually ________ towards the Earth but their “tangential” ________ keeps them moving in a circular orbit. Words – velocity, orbits, accelerating, natural, artificial

  8. Comets Comets are balls of dust and frozen gas. They have very elliptical orbits: What happens to the speed of the comet when it approaches the sun and why?

  9. More information on gravity If you double the distance the gravitational force divides by 4… If you triple the distance the force divides by 9… The amount of gravity attracting an object decreases the further out the object is… F F/4 F/9

  10. Artificial Satellites Geostationary orbits: Low polar orbits:

  11. Artificial Satellites Artificial satellites have been around for 50 years and have 3 main uses: 1) Observation (e.g. Hubble Space Telescope) – these are in orbit high above the Earth and can observe the universe without interference by the ____________ 2) Communications (e.g. ___, phone, car “SatNav” systems) – these satellites are in “geostationary” orbits. This means that the satellite always stays above ____ ____ point on the Earth and takes a ______ to complete an orbit 3) Monitoring (e.g. weather, spy satellites) – these satellites have a “___ _____” orbit and may scan around the Earth several times a day and travel _____. Words – the same, atmosphere, low polar, TV, day, faster

  12. P5b Vectors and Equations of Motion

  13. Speed vs. Velocity 04/01/2020 04/01/2020 This car is travelling at a speed of 20m/s This car is travelling at a velocity of 20m/s east Speed is simply how fast you are travelling… Velocity is “speed in a given direction”…

  14. Relative Speed 04/01/2020 04/01/2020 20mph Consider two cars driving past each other: 50mph What is the relative speed of the cars compared to each other?

  15. Circular Motion 04/01/2020 04/01/2020 1) Is this car travelling at constant speed? 2) Is this car travelling at constant velocity?

  16. Speed vs. Velocity Start -1 metre 1 metre Speed = Velocity = Speed = Velocity = Speed = Velocity = Speed = Velocity = “Speed” is how fast you go. “Velocity” is how fast in a given direction.

  17. Vector vs. scalar 04/01/2020 Scalar quantities have size (“magnitude”) only and no direction. Vector quantities have both size and direction. Scalar or vector??? Scalar Vector 8. Power 2. Distance 12. Acceleration 1. Mass 6. Energy 7. Time 3. Displacement 4. Speed 11. Force 10. Current 5. Velocity 9. Momentum

  18. Adding Vectors 04/01/2020 10km 10N 10km 100ms-1 5ms-1 Calculate the “resultant vector” for these pairs of vectors: 5N 14.1km 100.1ms-1

  19. Distance, Speed and Time revision Speed = distance (in metres) time (in seconds) S V T • Simon walks 200 metres in 40 seconds. What is his speed? • Howard covers 2km in 1,000 seconds. What is his speed? • How long would it take Ryan to run 100 metres if he could run at 12m/s? • Ben throws a book at Dan and it travels at 50m/s for 0.2s. How far away was Dan? • Chris is learning to drive. He drives his car at 85mph (about 40m/s). How long does it take him to drive 20km?

  20. Equations of Motion u + v s = t 2 v = u + at s = ut + ½at2 v2 = u2 + 2as

  21. Some hard questions • Ben drops a ball on Dan’s foot. How long does the ball take to fall 1m? 2m? Why is the second answer not twice the first? • Ryan flies to Belgium. His aeroplane has a maximum acceleration on the ground of 3.4ms-2. What is the minimum length of runway needed to reach its take off speed of 110ms-1 and how long will this take? • Luke likes watching kangaroos. A kangaroo jumps to a vertical height of 2.8m. For how long was it in the air? • Tom likes baseball. A baseball pitcher can release a ball at 40ms-1 after accelerating through a distance of 2.5m. Calculate the average acceleration of the ball.

  22. P5c Projectile Motion

  23. Vertical Projection 04/01/2020 If I throw this ball upwards with a speed of 40ms-1 how high will it go? Use v2 = u2 + 2as 0 = 402 + (2 x -9.81 x s) 0 = 1600 – 19.62s 1600 = 19.62s s = 1600/19.62 s = 81.5m

  24. Practice Questions 04/01/2020 • How far will a cricket ball go if it is thrown upwards with an initial velocity of 10ms-1? • How far will a table tennis ball go if it is thrown upwards with an initial velocity of 5ms-1? • A human cannonball is projected vertically upwards and she reaches a vertical height of 20m before coming back down. How fast was she going when she left the cannon? • A test tube falls off the table. If the table is 1m high how fast was the test tube going when it hit the floor?

  25. Projectile Motion Aha! If I let go of the branch when he fires his gun I’ll be safe because the bullet will go above me… This curved path is called a “trajectory” and its shape is “parabolic”.

  26. Analysing Projectile Motion Throughout this motion the horizontal velocity stays the same: The vertical velocity changes due to the effect of gravity:

  27. Projectile Motion 1.5m 50m Question – how long did this take and how fast was the bullet? • Use x = ut + ½at2 vertically to find the time • Then use speed = distance / time horizontally to get the speed

  28. Example questions • Ben throws a bowling ball at Tom and it lands on his foot. If the ball started 1.2m above Tom’s foot and the distance between them was 2m calculate both the time taken and the initial velocity of the ball. • Rob fires a gun and the bullet leaves the barrel at a speed of 200ms-1. If it landed on the ground 500m away calculate how long the journey took and how high up Rob was holding the gun from ground level. • Andrew likes knocking test tubes off the table. If he hits one with an initial velocity of 2ms-1 and the table is 1m high calculate the time taken for the test tube to hit the floor and how far away from the table it landed.

  29. Recap questions • Andrew Murray hits a tennis ball and it passes horizontally over the net and lands just inside the baseline of the court. The net has a height of 1.07m and is 11.9m from the baseline. Find the horizontal speed of the ball. • Ronaldo takes a free kick and it flies into the top corner horizontally. If the corner is 2.4m above the ground and the goal is 18m away calculate the time taken for the ball to reach the goal.

  30. Projectile Motion in Sport When playing golf, football, throwing a javelin etc the range clearly depends on the angle. What is the best angle for the longest range?

  31. P5d Action and Reaction

  32. Action and reaction Newton 1642-1727 When body A exerts a force on body B, body B exerts an equal and opposite force on body A. My third law of motion! My third law says that if I push to the right I will move backwards as well.

  33. Action and reaction What will happen if I push this satellite away from me?

  34. Action and reaction Consider a man standing on the Earth:

  35. Momentum Momentum = Mass x Velocity P (in kgms-1)(in kg)(in ms-1) M V Any object that has both mass and velocity has MOMENTUM. Momentum (symbol “p”) is simply given by the formula: • What is the momentum of the following? • A 1kg football travelling at 10ms-1 • A 1000kg Ford Capri travelling at 30ms-1 • A 20g pen being thrown across the room at 5ms-1 • A 70kg bungi-jumper falling at 40ms-1

  36. The Conservation of Momentum In any collision or explosion, momentum is conserved. Here is an example: Before I fired this gun I had no momentum. This means that after I fired the gun I must also have no momentum. Therefore, if the bullet goes forwards, I will have to move backwards to balance the bullet’s momentum.

  37. Conservation of Momentum 04/01/2020 Speed = 50ms-1 Speed = 20ms-1 Speed = ??ms-1 In any collision or explosion momentum is conserved (provided that there are no external forces have an effect). Example question: Two cars are racing around the M25. Car A collides with the back of car B and the cars stick together. What speed do they move at after the collision? Mass = 1000kg Mass = 800kg Mass = 1800kg Momentum before = momentum after… …so 1000 x 50 + 800 x 20 = 1800 x V… …V = 36.7ms-1

  38. Momentum in different directions 04/01/2020 Speed = 20ms-1 Mass = 1000kg Mass = 800kg Speed = 50ms-1 What happens if the bodies are moving in opposite directions? Momentum is a VECTOR quantity, so the momentum of the second car is negative… Total momentum = 1000 x 50 – 800 x 20 = 34000 kgms-1 Speed after collision = 34000 kgms-1 / 1800 = 18.9ms-1

  39. More questions… 04/01/2020 • A white snooker ball moving at 5ms-1 strikes a red ball and pots it. Both balls have a mass of 1kg. If the white ball continued in the same direction at 2ms-1 what was the velocity of the red ball? • A car of mass 1000kg heading up the M1 at 50ms-1 collides with a stationary truck of mass 8000kg and sticks to it. What velocity does the wreckage move forward at? • A defender running away from a goalkeeper at 5ms-1 is hit in the back of his head by the goal kick. The ball stops dead and the player’s speed increases to 5.5ms-1. If the ball had a mass of 500g and the player had a mass of 70kg how fast was the ball moving? • A gun has a recoil speed of 2ms-1 when firing. If the gun has a mass of 2kg and the bullet has a mass of 10g what speed does the bullet come out at?

  40. Another example α 241 237 Am Np 4 95 93 2 Consider the nuclear decay of Americium-241: The momentum before the decay was zero, so the Neptunium atom and alpha particle must have equal and opposite momentum.

  41. Particle Motion in Gases Gas pressure is caused by particles hitting the side of a container. Anything we do that increases those collisions will increase the pressure: These collisions mean that the particles are changing in momentum every time they hit the sides of the container. Therefore the side of the container is exerting a force back on the particles.

  42. Particle Motion in Gases Consider decreasing the volume: The particles should collide with the sides of the container _____ often, therefore the pressure is ________.

  43. Particle Motion in Gases Now consider increasing the temperature as well: The particles should collide with the sides of the container _____ often, therefore the pressure is ________. This could cause the container to ______.

  44. Another example Rockets use the ideas of ______ and Newton’s third law. The gas is under high _______ which means the particles are pushed out with a large ______. The particles therefore exert an equal and opposite reaction on the rocket, pushing it upwards. To launch a satellite into space, a ______ force is needed so you’ll need lots of ____ and it should be under high pressure. Words – fuel, momentum, large, force, pressure Consider a rocket:

  45. P5e Satellite Communication

  46. Diffraction 04/01/2020 Diffraction is an effect seen when a wave travels around a corner or through a narrow gap: More diffraction if the size of the gap is similar to the wavelength More diffraction if wavelength is increased (or frequency decreased)

  47. Artificial Satellites Satellites use digital microwaves to send us communications: Geostationary satellites use higher frequency waves Low polar satellites use lower frequency waves The satellite dish needs to be pointed exactly at the satellite as the microwaves are not diffracted much due to the size of the transmitter on the satellite being much bigger than the wavelength of the microwaves.

  48. Analogue vs. Digital Signals 04/01/2020 + 1 - 0 Analogue signals (like talking or music) continually vary in amplitude and/or frequency Digital signals, however, are either off or on, and the information is sent in a series of pulses • There are two main advantages of digital: • More information can be sent down the same cable • Better quality, because a digital signal can be amplified without amplifying the extra noise:

  49. Radio Waves Some radio waves (frequencies between 30Mhz and 30GHz) pass through the Earth’s atmosphere – therefore microwaves are used to communicate with satellites. Some radio waves (above 30GHz) are absorbed or scattered by the rain and dust in the atmosphere. Some radio waves are reflected by the atmosphere (they have a frequency below 30MHz).

  50. Diffraction of Radio Waves A high frequency (short wavelength) wave doesn’t get diffracted much – the house won’t be able to receive it…

More Related