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

Potential –Stored energy based on position; energy that can do work Kinetic –Energy of motion; energy doing work Transformation of Energy 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 1 st – objects in motion stay in motion at a constant velocity and objects at rest stay at rest unless another forces acts on it 2 nd – F=ma 3 rd – 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 Motion Speed Acceleration A push or pull on an object; has a size and direction Movement; change in an object’s position over time Distance traveled over time; distance divided by time 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? What is its acceleration? Speed = d/t = 600 m/30 s = 20 m/s 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/s 2 F = ma 25 N = 0.5 kg x a a = 25 N / 0.5 kg a = 50 m/s 2 REMINDER 1 N = 1 kgm/s 2

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 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 Work = Fd (force x distance) Work = 20 N x 10 m Work = 200 N·m

Simple Machines lever pulley screw wheel & axle

More machines… inclined plane wedge

Waves compression wave transverse wave

Wave parts crest trough wavelength amplitude

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… surface wave s-wave p-wave

Wave Review Compression wave Transverse wave Ocean 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???