Transcript TAKS Review
TAKS Review Objective 4 The student will demonstrate an understanding of motion, forces, and energy. Transformation of Energy • Energy comes in what forms? – Heat, chemical, mechanical, & electrical • Creating electricity from geothermal, wind, burning of fossil fuels, hydroelectric, nuclear, etc. by changing forms • Law of Conservation of Energy— energy is neither created nor destroyed, it can change forms Transformation of Energy • Potential – Stored energy based on position; energy that can do work • Kinetic – Energy of motion; energy doing work On the next slide, explain where the ball has potential and kinetic energy. Also, where is kinetic energy the lowest and the highest? Newton’s Laws • 1st – objects in motion stay in motion at a constant velocity and objects at rest stay at rest unless another forces acts on it • 2nd – F=ma • 3rd – for every action, there is an equal but opposite reaction Balanced vs. Unbalanced • Balanced forces result in… – Objects at rest staying at rest – Objects in motion stay in motion at a constant velocity • Unbalanced forced result in… – Resting objects caused to move – Objects in motion change their speed and/or direction Motion Terms • Force A push or pull on an object; has a size and direction • Motion Movement; change in an object’s position over time • Speed Distance traveled over time; distance divided by time • Acceleration Change in speed over time; change in velocity divided by time to make change; + (speed up) or – (slow down) Calculations • A car has a mass of 900 kg. It travels 600 m in the same direction for 30 s at a constant speed. What is its speed? Speed = d/t = 600 m/30 s = 20 m/s • What is its acceleration? Acceleration is a change in speed; since the car is traveling at a “constant speed”, its acceleration is zero. Calculations • A rock is thrown from a bridge 15 m above the river with a 2.5 N force. It has a mass of 0.5 kg. What is the acceleration of the rock? F = ma 25 N = 0.5 kg x a a = 25 N / 0.5 kg a = 50 m/s2 REMINDER 1 N = 1 kgm/s2 Calculations • A Southwest airplane travels at a rate of 7 km/min at a height of 18,000 m above the Earth’s surface. How long will it take to travel from Dallas to San Antonio which is 315 km away? Speed = d / t 7 km/min = 315 km / t t = 315 km / 7 km/min t = 45 min Calculations • Your classroom is 4 m by 6 m and each desk is 1.5 m by 1 m. How much work would you have to do to move a desk 10 m if you apply a force of 20 N? Work = Fd (force x distance) Work = 20 N x 10 m Work = 200 N·m Simple Machines lever screw pulley wheel & axle More machines… inclined plane wedge Waves compression wave transverse wave Wave parts crest wavelength amplitude trough More waves • Number of waves that pass a given point per unit of time is frequency • In sound, frequency is related to pitch – High frequency = high pitch – Low frequency = low pitch Electromagnetic Waves • Transverse waves that travel through space; radiant energy • The EM spectrum: Ocean Waves • Caused by wind • Amplitude called “wave height” • As waves approach the shore, wavelength decreases and wave height increases until it “breaks” as it nears the shoreline Seismic Waves • • • • Caused by earthquakes Measured with seismographs Move through the crust of the Earth Primary (P), Secondary (S), and Surface or Longitudinal (L) waves • P-waves are fastest and move in compressions • L-waves are slowest and move earth up and down Seismic Wave demo… P wave S wave Surface wave Seismic Waves… s-wave p-wave surface wave Wave Review Compression wave Ocean wave Transverse wave Surface wave Reminders… • Energy is not created nor destroyed; it is only converted from one form to another; i.e., chemical heat mechanical electrical • Potential energy is energy of position; kinetic energy is energy of motion • Forces affect motion and speed • There are different types of waves that travel through different media »Any questions???