Physics PSSA Review - Presentation

1. Physics PSSA Review - Presentation

2. Energy Sources & Transfer of Energy PSSA Eligible Content S11.C.2.1.

3. RADIATION • Radiation is energy in the form of electromagnetic waves. • An electromagnetic wave is a sequence of alternating electric fields & magnetic fields that travel through space. • This wave is caused by a vibrating charge.

4. Properties of Electromagnetic (EM) Waves • The crest is the highest point of the wave. • The trough is the lowest point of the wave. • Wavelength is the distance between two successive troughs or crests. • Frequency is the number of waves that pass a certain point in a given time. It is measured in Hz, where 1 Hz = 1 wave per second.

5. Electromagnetic Spectrum • The collection of all electromagnetic frequencies is known as the electromagnetic spectrum. • In the image below, note that frequency increases as wavelength decreases. • The higher the frequency, the more energy the wave has.

6. Difference between Sound Waves & Electromagnetic Waves • Sound waves need a medium to travel through while EM waves do not. • ALL EM waves travel at the speed of light, regardless of frequency, while sound waves travel much slower.

7. Difference between Sound Waves & Electromagnetic Waves (cont’d) • EM waves are transverse waves while sound waves are longitudinal waves. • A transverse wave is one where the wave oscillates (vibrates) perpendicular to the direction the wave is moving. • A longitudinal wave is one where the wave oscillates parallel to the direction the wave is moving.

8. Energy • Energy is the ability to do work. • Some forms of energy include: • Mechanical energy (e.g., a car moving) • Chemical energy (e.g., stored in batteries) • Sound energy (e.g., music) • Energy cannot be created or destroyed, but can be converted from one form to another … this is a statement of the law of conservation of energy.

9. Kinetic Energy • Kinetic energy is the energy associated with the motion of an object. • Kinetic energy (KE) is calculated by multiplying one-half an object’s mass by its velocity squared. • Therefore, increasing the velocity of an object will increase its kinetic energy more than increasing its mass will.

10. Potential Energy • Potential energy is energy stored within an object due to its position or composition. • Potential energy (PE) is calculated by multiplying the mass (m)of an object by the acceleration due to gravity (g =9.8 m/s2) & the height it is lifted (h) • A stick of dynamite not in use also has potential energy due to its chemical composition. The potential energy is converted to kinetic energy when the dynamite explodes.

11. Energy Conversions & rocket Propulsion • How is a rocket propelled into space from the launching pad? • Fuel is ignited. • Chemical reaction occurs that causes gases to be released with great force. • Chemical energy is converted to kinetic energy. • The moving gases exert an upward force that pushes the rocket up toward space.

12. Electric Current • Electric current is the continuous flow of electric charges. It is measured in amperes (A), or amps. • Electrons flow from a region of higher potential energy to a region of lower potential energy. • The difference in potential energy between 2 locations is known as potential difference, or voltage (V). It is measured in volts (V). • Potential difference results from differences in the electrical charges between 2 locations. • A battery is a device that converts chemical energy to electric potential energy.

13. Circuits • A circuit is a closed path through which electricity can flow. Wires (conductors) Switch Battery (voltage source) Bulb (resistor)

14. Types of Circuits • Series circuits provide only one possible path for the flow of current. • Parallel circuits provide multiple pathways for the flow of current.

15. Ohm’s Law • The relationship between current (I), voltage (V), & resistance (R) is described by Ohm’s Law. • This law states that the greater the voltage across a device the greater the current through that device. Conversely, the greater the resistance across a device, the lower the current through it. • Mathematically, this law looks like this:

16. Ohm’s Law Example • A 9.0 volt battery is connected to a small light bulb. The resistance of the filament in the bulb is 3.0 Ω. How much current is flowing through the circuit?

17. Energy and the Environment PSSA Eligible Content S11.C.2.2.

18. Fossil Fuels • A fossil fuel is an energy source that formed over millions of years from the decayed remains of ancient plants & animals. • Examples of fossil fuels include coal, petroleum, and natural gas.

19. Advantages of fossil fuels • They release large amounts of energy when burned. • Transporting them to power stations is fairly easy. • They are easily stored.

20. DisAdvantages of fossil fuels • Require millions of years to form. • Must be obtained from inside Earth by drilling or mining. • This changes the landscape & causes erosion. • Disrupts habitats. • Drilling & mining also releases chemicals into the environment that pollute nearby water supplies. • Is dangerous for miners. • Burning fossil fuels releases large amounts of pollutants into the air. • Sulfur & nitrogen combine with water in the atmosphere to produce acid rain (pH < 5.6). • Carbon dioxide is released into the atmosphere. This CO2MIGHT contribute to global warming.

21. Nuclear energy • Nuclear energy is energy that is stored in the nucleus of atoms. • Nuclear power plants produce electrical energy from nuclear fission. • This is when the energy stored in the nucleus of an atom is released by splitting the atom into 2 smaller nuclei. • Nuclear fusion is the combining of light nuclei to make a heavier nucleus. Nuclear fission

22. Renewable versus nonrenewable energy resources • An energy resource is a natural resource that can be converted into a form of energy that can do useful work. • There are two types of resources: • Renewable resources – those whose supplies are either inexhaustible or can be replenished as quickly as they are used. • Nonerenewable resources – natural energy supplies that cannot be replaced as quickly as they are used.

23. Fossil fuels (coal, oil, natural gas) Solar energy Nuclear energy Wind energy Biomass Hydroelectric Geothermal Tidal Let’s take a deeper look at the renewable energy resources!

24. Solar Energy • Electromagnetic waves from the sun picked up by collectors & converted to thermal & electrical energy. • Advantages: • No air/water pollution. • Small systems are inexpensive. • Disadvantages: • Needs storage & backup. • Solar power plants are expensive.

25. Wind Energy • Energy obtained from moving air. • Advantages: • No air/water pollution. • Inexpensive to build or use. • Disadvantages: • Needs significant amount of wind and land.

26. Hydroelectric Energy • Energy obtained from the kinetic energy of moving water. • The water turns a turbine which generates an electric current. • Advantages: • No air/water pollution. • Inexpensive to build or use. • Disadvantages: • Harms natural habitats. • Good sites for dams are already in use.

27. Biomass Energy • Energy derived from organic matter. • Advantages: • Available in less developed countries. • Burning garbage reduces the amount in landfills. • Disadvantages: • Burning wood releases CO2. • Recycling landfill gas is expensive.

28. Tidal Energy • Energy derived from the kinetic energy of rising & falling ocean tides. • Advantages: • No air/water pollution. • Inexpensive to use. • Tides are reliable. • Disadvantages: • Few sites with strong enough tides.

29. Geothermal Energy • Energy derived from the heat that is within the Earth. • Advantages: • Little impact on the environment. • Inexpensive to use. • Takes up little space. • Disadvantages: • Can release hazardous gases into the air. • Few sites with adequate geothermal conditions.

30. PSSA Science Review Assessment Anchor S11.C.3.1 (Principles of Motion and Force)

31. Motion • The motion of an object is described by various quantities. • Distance • Velocity (Speed with direction) • Acceleration (Change in velocity) • Motion is often tracked using graphs.

32. Sample Motion Tables • The motion of an object can be tracked using a table. It relates time to either the distance or velocity variable.

33. Sample Motion Graphs Distance Velocity • Motion can also be tracked using the visual aid of a graph. In addition to the plot itself, the slope and area of the plot have significance. Time Time Rest Pos Velocity Constant Velocity Neg Acceleration Neg Velocity Pos Acceleration

34. Newton’s Laws of Motion • Newton’s laws govern the ways motion relates to forces present in a situation. • 1st Law: Law of Inertia (Equilibrium Situation) • 2nd Law: Net Force Causes Acceleration (Nonequilibrium Situation) • 3rd Law: Action and Reaction

35. Gravity and Weight 67kg • Weight is the force due to the presence of gravity. • This force causes objects to accelerate at the same rate, regardless of mass. 0.5kg

36. Conservation of Momentum • Momentum is the product of mass and velocity. • Total momentum is conserved (stays constant) in a closed and isolated system. • When objects collide, momentum may be transferred, but it is not lost.

37. Forces and Work • When a force is exerted over a distance, energy is consumed in the form of work. In simplest form, work is the product of force and distance.

38. Simple Machines • Simple machines are devices that multiply and/or redirect forces. • Input force is often called effort. • Output force is often called load or resistance. • Though they can make tasks easier, they never cause more work output than work input. This would violate the law of conservation of energy.

39. L E F The Six Major Simple Machines Lever Pulley Incline Plane Wedge Wheel & Axle Screw

40. Levers • A lever is a rigid shaft that pivots about a fixed point (fulcrum). Output force is called “load,” while the input force is often called “effort” • Levers are divided into 3 types or classes, depending on which component is centralized. • 1st Class (Fulcrum), 2nd Class (Load), 3rd Class (Effort) E L F

41. Moveable Pulley Fixed Pulley Pullies • Pulleys are grooved wheels usually mounted to fixed set of hooks. • Fixed pulleys redirect force. • Moveable pulleys multiply force. • A combination of pulleys does both. • The mechanical advantage of a pulley system can be determined by countin the number of supporting strings.

42. Wheel and Axle • The wheel and axle is composed of two concentric parts: a larger disk called the wheel and a smaller one called the axle. • Generally, the wheel represents the input while the axle represents the output. Wheel (Input) Axle (Output)

43. Mechanical Advantage • Mechanical advantage is the ratio between the output force of a machine and the input force.

44. Efficiency • Efficiency is the percentage ratio of useful work output to work input.

45. Compound Machines • A compound machine is a combination of two or more simple machines. • Examples of compound machines include: • Bicycles • Can Openers

46. Electrostatics • Electrical Charge is present in matter. It can be separated by the exertion of work and then used.

47. Magnetism • Certain materials, such as iron, nickel, and cobalt, are magnetic due to their electron configurations. • These produce magnetic fields, which allow for magnetic forces to occur.

48. Electricity and Magnetism • Moving electric charge induces a magnetic field. • This principle is what allows for electromagnets and electric motors to work.