Physical Science

1. Physical Science Review One: Physics

2. VELOCITY This snowboarder jumps 12 meters in 1.5 seconds. What is his velocity? DISTANCE TIME VELOCITY= v= 12 m 1.5 s = 8 m/s forward

3. Acceleration This bullet train is traveling 125 m/s when it begins to slow down. When it is finished slowing down it is only going 88 m/s. If it takes the train 25 seconds to slow down, what is the trains acceleration? final velocity-initial velocity change in time Acceleration = Vf - Vi t a= 88 m/s – 125 m/s 25 s a= a= -1.4 m/s2 forward

4. Acceleration: Finding Final Velocity This bicyclist started at rest and accelerated at a rate of 3 m/s2 for 10 seconds. What is his final velocity? Vf= initial velocity + (acceleration x time) Vf= 0 m/s + (3 m/s2 x 10 s) Vf= 30 m/s forward

5. Newton’s Laws Law 1 All objects have inertia. Inertia is the tendency of an object to stay at rest or in motion until a force acts upon it. An objects inertia is based on its mass. Law 3 For every actionforce there is an equal and opposite reactionforce. The hammer and nail are pushing on each other with the same force. Law 2 The force that an object is experiencing is the product of its mass and acceleration. F=ma

6. All objects have gravity. The force of gravity depends on the mass of an object. The more mass the object has, the more gravity that it has. Also the distance between two objects will determine how great the force of gravity is on those objects. The greater the distance, the less the gravitational force. The closer they are, the greater the force of gravity. Gravity This golf ball has gravity, but not nearly as much as the Earth does…

7. Mass, Weight, and Gravity An object’s mass is different than its weight. An objects weight is based on how much gravity is pulling on the object. In other words, an object’s weight will change depending on what planet it is on. Weight is measured in Newtons. An objects mass never changes. Mass is measured in grams or kilograms

8. 12 kg Force Every object will fall at the same acceleration due to gravity: 9.8 m/s2. If this bowling ball and golf ball are dropped at the same time, they will hit the ground at the same time. However, the bowling ball will hit with more force (F=ma). With what Force do these objects hit the ground? 0.25 kg

9. Force

10. Work Work = Force x Distance W=Fd Work is measured in Joules Pg. 285 Practice #1-5

11. Power = Work / Time P= W/t Power is measured in Watts Power Pg. 287 Practice #1-5

12. Mechanical Advantage How easy is the work that you are doing? MA= input distance / output distance MA= output force / input force

13. Simple Machines make work EASIER! You still do the same amount of work, it is just spread out over a longer distance.

14. Simple Machines Each rope pulling up against the weight counts as 1 MA. Anything greater than 1 is considered “easier work.”

15. Simple Machines Steeper ramps have less mechanical advantage than lower ones. 7 feet 3.5 feet 3 feet 3 feet

16. Simple Machines More leverage allows for more Mechanical Advantage. The farther the distance your effort is from the fulcrum, the easier the work is. In other words, the longer the handles are on a wheelbarrow, the easier it is to lift the load. Also, the farther away from the hinges the door knob is, the easier it is to open the door.

17. Energy Transformation

18. Kinds of Energy

19. Energy Transformations light chemical nuclear light/heat mechanical/heat chemical

20. Transferring Heat Radiation Convection Conduction

21. Specific Heat Specific Heat is the amount of heat energy that a substance can absorb before it changes temperature. Conductors have a low specific heat, while insulators have a high specific heat. Water has a very high specific heat, which is why the pool is cold in the middle of summer.

22. Specific Heat Formula c = _Q Specific Heat = Change in Heat Energy Mass x Temperature Change m x T Pg. 338 #6 Heat Lost or Gained in a System Heat gained or lost = mass x specific heat x temperature change Q=mc T Pg. 338 #1-3

23. Waves A wave is a transfer of energy because of an oscillation (vibration). The heads of these bongos are vibrating and making sound waves. The atoms in this light bulb are vibrating and making light waves.

24. Waves

25. Waves LargerWavelength LowerFrequency LowerEnergy SmallerWavelength HigherFrequency HigherEnergy

26. Waves Waves can be mechanical or electromagnetic.

27. Waves Waves can be transverse or longitudinal.

28. LOUD Sound is a mechanical, longitudinal wave. QUIET LOWER FREQUENCY HIGHER FREQUENCY HIGH PITCH LOW PITCH

29. The speed of sound depends on the temperature and density of the medium. Temperature Speed of Sound Density

30. Light Light is a transverse, electromagnetic wave. Light travels at 300,000,000 m/s. (3.0 X108 m/s)

32. Reflection Waves bounce off of a barrier.

33. Refraction Waves change direction slightly when they enter a new medium.

34. Interference Waves affect each others amplitudes.

35. Diffraction Waves bend around a barrier.

36. Electricity and Magnetism Atoms have electron clouds. Those electrons can cause an object to be magnetic. Also, if the protons and electrons of an object are out of balance, the object can become charged. Electric charge can move and create electric current. Electric current is energy that can be useful to people.

37. Electric Charge - - Electric charge can occur because of contact (conduction) or just by being close (induction). - - - - - + + + + +

38. Static Electricity vs. Current Electricity DC Static electricity is when an electric charge sits on a surface. When the charge moves to equilibrium, it is called a discharge. Current electricity is a flow or vibration of electric charge over a distance. This can be a direct current (DC) or an alternating current (AC). - - - - - - - + + + + + AC

39. Current Current is the flow of electricity. It is measured in Amps (A). Voltage is the potential electrical energy. It is measured in Volts (V). Resistance is the resistance to current. It is measured in Ohms (O). AC

40. Waterfall example

41. Circuits Parallel Circuit Series Circuit If one goes out, the others may stay on (as long as there is a complete circuit from one end of the battery to the other). If one goes out, they all go out.

42. Calculating Voltage V=IR Voltage = Current X Resistance Volts = Amps X Ohms Yellow Book Pg. 443 #3

43. Magnetism Magnets have a magnetic field around them. The positive field is a “push” field, and the negative is a “pull” field. Opposite fields attract, and like fields repel.

44. Electromagnetism The “right hand rule” can be used to determine the direction of the electric field. Electric current sent around a metal object can make the object become an electromagnet.

45. Electromagnetism The basic set-up for a generator or electromotor. If electric current is used to make magnets spin, it is called an electromotor. If spinning magnets are used to make electric current, it is called a generator.

46. Electromagnetism Electric power plants use generators to make alternating current (AC). The trick is to get the magnets to spin (turbines). Steam works well, but making water boil is also tricky, because burning coal makes pollution. Radioactive material can also heat up water (nuclear power), but radiation is dangerous. Falling water also does the trick (hydroelectric), but you have to have the right environment for falling water.