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# Physics power point

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• ### Physics power point

1. 1. Relative Velocity and Frame of Reference<br />
2. 2. Frame of Reference<br />Motion is a change in position relative to a frame of reference<br />Frame of reference: a set of objects used to measure a change in position.<br />Standing frame of reference<br />Moving frame of reference.<br />
3. 3. Speed vs Velocity<br />Speed is the distance an object travels in a time period.<br />S = d/ t <br />Units m/s<br />Velocity of an object is the speed and direction of motion.<br />Ex: A car travels 60 m/s north on I-75 and then turns around and goes south at 60 m/s. Does the car have the same speed? Same velocity?<br />Ans: Same speed, different velocities b/c different directions<br />
4. 4. Relative Speed/ Velocity<br />Relative speed and velocity depend on a frame of reference.<br />Standing frame of reference<br />Objects moving in the same directions, add (+) speeds<br />Objects moving in opposite directions, subtract (-) speeds<br />
5. 5. Relative Speed/ Velocity<br />Moving frame of reference<br />Objects moving in the same directions, subtract (-) speeds<br />Objects moving in opposite directions, add (+) speeds<br />
6. 6. Calculating Relative Speed Flowchart<br />
7. 7. Newton’s Gravitational Force<br />
8. 8. Force of Gravity<br />Gravitational force – attractive force that any two objects having a mass exert on each other.<br />On Earth, gravitational force is equal to the mass of the object times the gravitational constant (accelaration)<br />F = mg<br />Units = kg m/s2 newtons (N)<br />Earth average g= 9.81 m/s2<br />Gravitational force = weight<br />
9. 9. Review <br />Mass vs. Weight<br />Mass – amount of matter in an object<br />Units = kilogram (kg)<br />Weight- how heavy something is. ( gravity applied on the mass of an object) <br />Units = Newton (N) <br />Newton is a derived unit (kg m/s2 )<br />
10. 10. Universal Law of Gravitation<br />Universal Law of Gravitation(ULG) – used to describe attractive force between large objects such as the planets and the sun.<br />G has constant value of 6.67 x 10-11 N m2/kg2<br />m1 = mass of object 1<br />m2 = mass of object 2<br />d = distance between two objects<br />
11. 11. Using the ULG<br />Ex: A satellite orbits Earth at a distance of 72 km. If the satellite were to orbit Earth at a distance of 144km away from the center of the Earth, by how much would the force between the satellite and the Earth change.<br />The force would be 4 times greater<br />The force would be 2 times greater<br />The force would be 2 times smaller <br />The force would be 4 times smaller<br />
12. 12. Using the ULG<br /><ul><li>Solution:</li></li></ul><li>Proportions<br />Proportions are relationships between two or more things.<br />To find relationships divide (÷)or create a ratio (fraction)<br />Direct relationships are shown as follows<br />X = Y<br />If x increases, y increases<br />Inverse relationships<br />X = 1/Y<br />If Y increases, X decreases<br />
13. 13. Using the ULG<br />Ex2: Two one kg spheres are 1 meter apart. Which of the following would double the gravitational force between them?<br />Doubling the mass of one sphere<br />Doubling the mass of both spheres<br />Halving the distance between both spheres<br />Doubling the distance between both spheres<br />
14. 14. ULG<br />Ex3: Two 20 kg spheres are 15 meters apart. Which of the following will give a gravitational force that is ¾ of the original force?<br />Double both masses, leave the distance the same.<br />Triple one mass, double the distance between them<br />Triple both masses, double the distance between them<br />Double both masses, double the distance between them. <br />
15. 15. Energy<br />
16. 16. Types of Energies<br />Radiant Energy- energy from the sun in <br />the form of electromagnetic waves (light)<br />Electrical Energy – energy of flowing<br /> electric particles, current.<br />Heat Energy – energy transferred by <br /> a difference in temperature<br />Chemical Energy – energy given off by chemical reactions<br />
17. 17. Types of Energies<br />Kinetic Energy – energy that an object has due to its motion<br />KE = ½ mv2<br />Units = kg m2/s2 Joules (J)<br />Potential Energy – stored energy that an object has due to its position<br />PE = mgh<br />Units = kg m/s2 m  Joules (J)<br />
18. 18. Types of Energies <br />Mechanical energy – energy used to perform work<br />Practice <br />
19. 19. Energy Transformations<br />During phase <br />changes, energy <br />is either absorbed <br />or released.<br />
20. 20. Energy Flow & Transformation<br />Energy from the sun is <br />captured by the green plants, <br />(trophic level I)transformed<br />into chemical energy <br />through photosynthesis <br />and passed on through the <br />various trophic levels. <br />The flow of energy is <br />unidirectional i.e., non-cyclic. <br />Some energy is lost in the<br />form of heat at every state<br />in the atmosphere.<br />Energy pyramid<br />
21. 21. 9. Buzz Lightyear is on a mission to save his home planet Galactika. A giant blazing meteor with a mass of 2.5 x 10^8 kg is creeping dangerously close to Galactika, whose mass is of 5.56 x 10^23 kg. It is currently at a distance of 6.99 x 10^3 km from his planet. Woody helped Buzz create the Mega Meteor Blaster to save Galactika. If Buzz uses the blaster on the meteor it will decrease the mass of the meteor by 4 but also push the meteor closer to the planet, cutting the distance between Galactika and the meteor in half. Time is ticking and Buzz needs your help to decide if he should use the Mega Meteor Blaster. Should he use the Blaster and what would happened to the force between Galactika and the meteor if he did? <br />