Many students had difficulty with the homework problems. Rather than just go over them, I did two sample problems on the board, similar to Problem 45 in the homework, always emphasizing the problem solving strategy. After that, I set up problem 48 and students worked out the answer.
I gave the students the rest of the period to work on either the HW problems from last night or problems 2 and 4 from the front side of the HW packet.
Monday, November 8, 2010
Wednesday, Nov 17, 2010
Go over Problems 3,8,9,14,24 from Applying Newton's Laws worksheet.
It is important to follow the problem solving strategy, draw the free-body diagram, from the free-body diagram write Newton's second law, and then do the math.
Force plate demo: Ask students to predict what the Force vs Time graph would look like for someone jumping up into the air. Sketch predictions on whiteboard.
Do demo - discuss.
Go over elevator problems on whiteboard.
Do football problem with angles. Show that applying upward as well as forward force decreases normal force and allow the player to knock the other over more easily. Showed graph of acceleration vs angle for various coefficients of friction.
Applications of Newton's Laws Worksheet. Work problems 2,4.
Assigned 42, 43, 44, 45, 48 on back side for tomorrow.
Last day to hand in CD 6 is Friday.
Students were having lots of problems with the problem solving strategy for Newton's Laws. I think I will postpone the test until next week instead of Friday.
It is important to follow the problem solving strategy, draw the free-body diagram, from the free-body diagram write Newton's second law, and then do the math.
Force plate demo: Ask students to predict what the Force vs Time graph would look like for someone jumping up into the air. Sketch predictions on whiteboard.
Do demo - discuss.
Go over elevator problems on whiteboard.
Do football problem with angles. Show that applying upward as well as forward force decreases normal force and allow the player to knock the other over more easily. Showed graph of acceleration vs angle for various coefficients of friction.
Applications of Newton's Laws Worksheet. Work problems 2,4.
Assigned 42, 43, 44, 45, 48 on back side for tomorrow.
Last day to hand in CD 6 is Friday.
Students were having lots of problems with the problem solving strategy for Newton's Laws. I think I will postpone the test until next week instead of Friday.
Tuesday Nov 16, 2010
Stamped homework, RA 4.4.
Went around room asking what students learned from Friday's class. Wrote answers on board.
Went over worksheet as a review of Monday's demos.
Collected RA 4.4 and any CD 6.
Showed clips from Independence Day video. Physics is everywhere...except Hollywood. Hollywood does not understand Newton's 3rd Law. Showed results of calculations for reaction force.
Suppose you have a jar of flies on an electronic balance and all the flies are sitting on the bottom. How would the scale reading change if the files took off and few around the jar. Referred to finger in water demo - the scale reading would not change.
Demo with flying saucer on force plate - same reading when it is resting on plate as when it is hovering above it.
Read Horse Sense.
Showed that it is not possible to apply a force of 200 N to a piece of paper held in front of you. We estimated the mass, time, distance and calculated the acceleration and force - much less than 1 N.
Go over kicking football problem.
Applications of Newton's Laws Worksheet. Work problem 3 on front after giving students a chance to think about it. Students did a similar problem but with different masses for the blocks.
Applying Newton's Laws Worksheet. Assigned problems 3,8,9,14,24
Went around room asking what students learned from Friday's class. Wrote answers on board.
Went over worksheet as a review of Monday's demos.
Collected RA 4.4 and any CD 6.
Showed clips from Independence Day video. Physics is everywhere...except Hollywood. Hollywood does not understand Newton's 3rd Law. Showed results of calculations for reaction force.
Suppose you have a jar of flies on an electronic balance and all the flies are sitting on the bottom. How would the scale reading change if the files took off and few around the jar. Referred to finger in water demo - the scale reading would not change.
Demo with flying saucer on force plate - same reading when it is resting on plate as when it is hovering above it.
Read Horse Sense.
Showed that it is not possible to apply a force of 200 N to a piece of paper held in front of you. We estimated the mass, time, distance and calculated the acceleration and force - much less than 1 N.
Go over kicking football problem.
Applications of Newton's Laws Worksheet. Work problem 3 on front after giving students a chance to think about it. Students did a similar problem but with different masses for the blocks.
Applying Newton's Laws Worksheet. Assigned problems 3,8,9,14,24
Monday Nov 15, 2010
Hand back and go over Newton's Laws test
Test Friday on harder Newton's 2nd Law Problems and Newton's 3rd Law Problems
Newton's 3rd Law introductory lecture:
Inanimate objects can exert elastic forces: demo with rubber band, laser beam on wall.
No such thing as an isolated force - forces come in pairs (pears)
Newton's 3rd law recipe: A acts on B, B acts on B
Demo with finger in water.
Demo with force sensors. A can't pull harder on B than B pulls on A.
Newton's 3rd Law: If object A exerts a force on object B, then B exerts a force on A that is equal in magnitude and opposite in direction.
Tug-of-War: A and B. The one who wins the tug-of-war is the person who pushes harder against the ground.
Action/Reaction forces never cancel out because they do not act on the same object. Because they do not act on the same object, they never appear in the same free body diagram.
Examples of action reaction pairs. Contrast with forces that are equal in magnitude but opposite in direction but are NOT action reaction pairs.
Action and Reaction for Different Masses: If you drop a ball, why does the ball fall down and not the Earth fall up? Same magnitude force = m A = M a. Ball has much less mass so it has larger acceleration. Earth has huge mass, tiny acceleration.
Magic tube: tube exerts upward force on ball, ball exerts downward force on tube. We can measure this extra force using a force sensor and, if the ball is falling at terminal velocity, determine the weight of the ball.
Hand out RA 4.4 due tomorrow
Hand out CD 6.1 due Friday for the last time
Test Friday on harder Newton's 2nd Law Problems and Newton's 3rd Law Problems
Newton's 3rd Law introductory lecture:
Inanimate objects can exert elastic forces: demo with rubber band, laser beam on wall.
No such thing as an isolated force - forces come in pairs (pears)
Newton's 3rd law recipe: A acts on B, B acts on B
Demo with finger in water.
Demo with force sensors. A can't pull harder on B than B pulls on A.
Newton's 3rd Law: If object A exerts a force on object B, then B exerts a force on A that is equal in magnitude and opposite in direction.
Tug-of-War: A and B. The one who wins the tug-of-war is the person who pushes harder against the ground.
Action/Reaction forces never cancel out because they do not act on the same object. Because they do not act on the same object, they never appear in the same free body diagram.
Examples of action reaction pairs. Contrast with forces that are equal in magnitude but opposite in direction but are NOT action reaction pairs.
Action and Reaction for Different Masses: If you drop a ball, why does the ball fall down and not the Earth fall up? Same magnitude force = m A = M a. Ball has much less mass so it has larger acceleration. Earth has huge mass, tiny acceleration.
Magic tube: tube exerts upward force on ball, ball exerts downward force on tube. We can measure this extra force using a force sensor and, if the ball is falling at terminal velocity, determine the weight of the ball.
Hand out RA 4.4 due tomorrow
Hand out CD 6.1 due Friday for the last time
Thursday, November 4, 2010
Monday, Nov 8, 2010
Review for test
Students worked analytic statics problem, 2 graphical statics problem, 2 worksheets on Newton's Laws, and then did the Quia quizzes
Students worked analytic statics problem, 2 graphical statics problem, 2 worksheets on Newton's Laws, and then did the Quia quizzes
Friday, October 29, 2010
Friday, Nov 5, 2010
Hand back Air Resistance Labs and go over.
Go over questions at end of chapter.
Allow students to work on worksheets, CD 5.1, Newton's Laws Problems
Answer questions on worksheets.
Go over questions at end of chapter.
Allow students to work on worksheets, CD 5.1, Newton's Laws Problems
Answer questions on worksheets.
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