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Pre-class Monday 1-23-12

Pre-class Monday 1-23-12. Solve the following equation for t: V f = V i + at. PHYSICS. Give back test and go over it Algebra review Covering 2 chapters this week (they are closely related) Begin ch 4: Forces. BIOLOGY. CHEMISTRY. Pre-class Tuesday 1-24-12.

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Pre-class Monday 1-23-12

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  1. Pre-class Monday 1-23-12 Solve the following equation for t: Vf = Vi + at

  2. PHYSICS • Give back test and go over it • Algebra review • Covering 2 chapters this week (they are closely related) • Begin ch 4: Forces BIOLOGY CHEMISTRY

  3. Pre-class Tuesday 1-24-12 What is the mascot for James Clemens’ high school?

  4. NEWTON’SFORCES • What is a force? • Push or pull exerted on an object • Vector • Variable: F • Newton’s 3 Laws of Motion

  5. NEWTON’S FIRST LAW • An object at rest tends to stay at rest. An object in motion tends to stay in motion in a straight line unless acted upon by an external force.

  6. NEWTON’S SECOND LAW F = m a

  7. FORCE F = ma F : force (Newtons, N) m : mass (kilograms, kg) a : acceleration (m/s2)

  8. NEWTON’S THIRD LAW • For every action there is an equal and opposite reaction.

  9. Launching Force Project • Objective • Apply the equations of motion and Newton’s Laws • Materials • 2-L bottle • Cardstock, tape, scissors, etc. • Deadlines • Construct in-class by Friday • Launch next Monday

  10. Pre-class Wednesday 1-25-12 How much force is required to accelerate a 10 kg mass at 5 m/s2? Hint: use THE equation from friday

  11. Types of Forces f T W

  12. WEIGHT W = mg W : weight (Newtons, N) m : mass (kilograms, kg) g : acceleration of gravity (9.8 m/s2)

  13. Net Forces • The total forces acting on an object • Draw free-body diagram to show forces • Ignore external forces • Keep X and Y directions separate SF=ma

  14. Examples of Free-body Diagrams

  15. Materials Lego kits Spring scales Masses Procedures Using the Lego kit, build a simple car or truck. Be sure it is large enough to hold some small masses and a place to attach the spring scale. Place the car on a level surface. Attach the spring scale to it. With a constant velocity, pull the car along the ground with the spring scale. Record the value of the force. Change the weight of the car by adding more masses. Repeat 3 times. Based on your results, what is the relationship between weight and applied force? Lego My Car

  16. Pre-class Thursday 1-26-12 How much does a 10 kg mass weigh? Hint: use one of the equations from yesterday

  17. Terminal Velocity • The maximum speed that can be obtained by a falling object • The force of gravity is equally balanced by the air resistance force (drag) • Constant speed, no acceleration

  18. Materials Meter stick Paper Stopwatch Scissors Procedures Drop a flat piece of paper 2 m. Measure the time for it to fall. Crumple the piece of paper into a loose ball. Measure time to fall in 2 m. Crumple the piece of paper into a tighter ball. Measure time to fall 2 m. Use the scissors to design your own paper object. Measure time to fall 2 m. Measuring Effects of Air Resistance What characteristic of the paper affected the falling time the most?

  19. 59. -9.8 N 61. 6,900 N 64. 250 kg 65. balloon, basketball, shot-put (b. reverse) 70. 250 N, bag does not hold 73. -14 m/s, 3185 N Top to bottom: 45 N, 57 N, 93 N 82. 138 m 89. 9.8 m/s2, 98 m/s, -49 N, 10 s 92. 37 N, 2.4 m/s2 CH 4 HW (p113-115)

  20. Pre-class for Wednesday 8-22-07 • Identify the forces on the crate by drawing a free-body diagram. Be sure to label each force and show its direction.

  21. F = ma f = m FN W = m g CHAPTER 4 &5 EQUATIONS SF=ma FN

  22. EQUILIBRIUM • Take attendance • Give back graded work • Go over home work problems • Finish chapter • If time, work on homework

  23. Materials Rubber bands Lego kits Ruler Masses Procedures Using the Lego kit, build a simple car or truck. Be sure it is large enough to hold some small masses and a place to attach a rubber band. Place the car on a level surface. Cut and attach a rubber band to it. Determine the length the rubber band stretches to get the car moving. Change the weight of the car by adding more masses. Determine the length the rubber band stretches in moving the car. Repeat 4 times. Without actually performing the experiment, describe for me (Be specific!) how you would determine the force needed to move the car. Lego My Car

  24. TEST OVER CHAPTER 5 • Take the time before the pep rally to study (about 20 minutes) • turn in homework before you leave for pep rally • return to this room, then we will go next door

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