Collected RA 5.2
Went around the room and asked what they learned from yesterday's class.
Handed back and quickly went over RA 5.1
Demo with blowpipes and marshmallows to show that longer cannons impart more impulse (same force, longer time) than short cannons.
Skare's demo with happy and sad balls knocking down block.
Conservation of momentum: If there is no net external force acting on a system then there is no change in momentum of the system.
It does not apply in all cases (such as falling object as system) but it has never been shown to fail.
Applied Conservation of Momentum to collisions:
Two basic types of collisions
1. Inelastic collisions: things stick
2. Elastic collisions: things bounce
If there is no net external force, momentum is conserved in both types of collisions.
Worked problem of inelastic collision on board.
Demo of inelastic and elastic collisions with air track.
Handed out Inelastic Collisions worksheet. Students worked on it in class and handed it in.
Handed out CD chpt 5 due for the last time next Wed. It asks for pictures, if you don't draw them then I will return the paper.
Handed out RA 5.3 due tomorrow.
Tuesday, November 25, 2008
Monday, November 24, 2008 - Blocks 1 and 3
Did not hand back Newton's Laws Test. Sub allowed students to go away and come back during lunch and/or after school to finish - something I never allow to happen.
Collected RA 5.1
Introduction to impulse and momentum lesson
Impulse = Fnet*time
Units of impulse = N s
Momentum = mass * velocity = inertia in motion = ooomph
Units of momentum = kg m/s
Derived Impulse = Change in momentum
Several examples of F*t for same change in momentum
Egg toss lab
Force plate demo - flex knees, lock knees
Bouncing gives greater impulse since there is a greater change in momentum. We know nothing about the force unless we know something about the time.
Handed out RA 5.2 due tomorrow - students had some time in class to work on it.
Collected RA 5.1
Introduction to impulse and momentum lesson
Impulse = Fnet*time
Units of impulse = N s
Momentum = mass * velocity = inertia in motion = ooomph
Units of momentum = kg m/s
Derived Impulse = Change in momentum
Several examples of F*t for same change in momentum
Egg toss lab
Force plate demo - flex knees, lock knees
Bouncing gives greater impulse since there is a greater change in momentum. We know nothing about the force unless we know something about the time.
Handed out RA 5.2 due tomorrow - students had some time in class to work on it.
Thursday, November 13, 2008
Friday, November 21, 2008 - Blocks 1 and 3
Went to science teachers' conference downtown.
Sub gave out test on Newton's 2nd and 3rd laws.
Students picked up RA 5.1 (IB) due Monday
Sub gave out test on Newton's 2nd and 3rd laws.
Students picked up RA 5.1 (IB) due Monday
Thursday, November 20, 2008 - Blocks 1 and 3
Collect RA 6.1 for the last time.
Answer any questions on end of chapter exercises and problems.
Discuss problems 2 and 4 on the front side of the Applying Newton's laws problem sheet.
Finish review for test on Friday.
Answer any questions on end of chapter exercises and problems.
Discuss problems 2 and 4 on the front side of the Applying Newton's laws problem sheet.
Finish review for test on Friday.
Wednesday, November 19, 2008 - Blocks 1 and 3
Students had lots of difficulty with the homework problems, mostly because they refused to follow the problem solving strategy and tried to take shortcuts but omitting steps.
I asked the students to work BY THEMSELVES on the problems and to raise their hands if they needed help. I really wanted the students to solve the problems by themselves and not just rely on my showing them how to do them or relying on one of their neighbors.
It took the entire period for them to complete the problem set so we did not have time to move on to the rest of the lesson. I assigned the end of the chapter questions and exercises for homework. Tomorrow I will go over any questions on those problems, look at problems 2 and 4 on the front side of the Applying Newton's Laws problem sheet and finish the review for the test on Friday.
Asked students to do end of chapter questions, chapter 4 for homework: Ex 17, 18, 19, 20, 24, 25, 26, 30, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 44, 48, 49, Prob 8
I asked the students to work BY THEMSELVES on the problems and to raise their hands if they needed help. I really wanted the students to solve the problems by themselves and not just rely on my showing them how to do them or relying on one of their neighbors.
It took the entire period for them to complete the problem set so we did not have time to move on to the rest of the lesson. I assigned the end of the chapter questions and exercises for homework. Tomorrow I will go over any questions on those problems, look at problems 2 and 4 on the front side of the Applying Newton's Laws problem sheet and finish the review for the test on Friday.
Asked students to do end of chapter questions, chapter 4 for homework: Ex 17, 18, 19, 20, 24, 25, 26, 30, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 44, 48, 49, Prob 8
Tuesday, November 18, 2008 - Blocks 1 and 3
Stamped and then went over RA 4.5, particularly the kicking football problem.
Handed back RA 4.4
Handed back homework problems 3,8,9 14,24
Students had difficulty with problem 8. Gave them some time in class to work on it and then went over it. 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.
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.
Applications of Newton's Laws Worksheet. Worked problem 3 after giving students a chance to think about it. Students did a similar problem but with different masses for the blocks.
Assigned 42, 43, 44, 45, 48 on back side for tomorrow.
Last day to hand in CD 6 is Thursday.
Handed back RA 4.4
Handed back homework problems 3,8,9 14,24
Students had difficulty with problem 8. Gave them some time in class to work on it and then went over it. 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.
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.
Applications of Newton's Laws Worksheet. Worked problem 3 after giving students a chance to think about it. Students did a similar problem but with different masses for the blocks.
Assigned 42, 43, 44, 45, 48 on back side for tomorrow.
Last day to hand in CD 6 is Thursday.
Monday, November 17, 2008 - Blocks 1 and 3
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 Friday'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.
Students did Horse Sense worksheet in class. Voted on best pictures.
Handed out RA 4.5 for homework due tomorrow.
Went around room asking what students learned from Friday's class. Wrote answers on board.
Went over worksheet as a review of Friday'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.
Students did Horse Sense worksheet in class. Voted on best pictures.
Handed out RA 4.5 for homework due tomorrow.
Friday, November 14, 2008 - Blocks 1 and 3
Collected HW problems 3,8,9,14,24 from Applying Newton's Laws worksheet.
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 (summary of class notes) due Monday.
Hand out CD 6, due for the last time on Thursday.
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 (summary of class notes) due Monday.
Hand out CD 6, due for the last time on Thursday.
Thursday, November 13, 2008 - Blocks 1 and 3
Students had some difficulties with the assigned HW problems. I gave students time in class to work on the problem set, and then went over some of them in class. Most students finished all the problems and checked their answers against my answer sheet.
Assigned problems 3,7,8,14,24 on Applying Newton's Laws problem sheet.
Assigned problems 3,7,8,14,24 on Applying Newton's Laws problem sheet.
Wednesday, November 12, 2008
Wednesday, November 12, 2008 - Blocks 1 and 3
Go over test.
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.
Show inclined plane problem first with no friction and then with friction. Show how to determine angles and use problem solving strategy.
Inclined plane cart demo: Ask students to predict what the displacement vs time, velocity vs time, and acceleration vs time graphs would look like for cart on track with motion sensor. Do they predict the same slope (acceleration) for the velocity vs time graph up and down? Show that the slopes are different because on the way up friction is opposite the component of weight but on the way down the friction force is along the component of weight. The net forces are different in both cases.
Show how we can actually calculate the coefficient of friction for the rolling cart.
Hand out Newton's Laws Practice Problems and Applying Newton's Laws problem sets. Assign problems 8,9,10,11 on Practice Problem sheet. Ask in particular that they do the problem on getting the car out of the mud. Do this problem on board first thing Thursday.
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.
Show inclined plane problem first with no friction and then with friction. Show how to determine angles and use problem solving strategy.
Inclined plane cart demo: Ask students to predict what the displacement vs time, velocity vs time, and acceleration vs time graphs would look like for cart on track with motion sensor. Do they predict the same slope (acceleration) for the velocity vs time graph up and down? Show that the slopes are different because on the way up friction is opposite the component of weight but on the way down the friction force is along the component of weight. The net forces are different in both cases.
Show how we can actually calculate the coefficient of friction for the rolling cart.
Hand out Newton's Laws Practice Problems and Applying Newton's Laws problem sets. Assign problems 8,9,10,11 on Practice Problem sheet. Ask in particular that they do the problem on getting the car out of the mud. Do this problem on board first thing Thursday.
Saturday, November 8, 2008
Friday, November 7, 2008 - Blocks 1 and 3
Test on Newton's First and the easier parts of Newton's 2nd Law.
I cut out some of the more difficult problems that I usually included and most students were able to finish easily.
No homework over the 4 day weekend.
I cut out some of the more difficult problems that I usually included and most students were able to finish easily.
No homework over the 4 day weekend.
Thursday, November 6, 2008 - Blocks 1 and 3
Finished review for test.
Assigned questions and problems from end of chapter. Students worked on these either alone or with partner. I then went over them.
I provided extra practice worksheets and answer keys for interested students.
Last day to hand in CD 5.1
Assigned questions and problems from end of chapter. Students worked on these either alone or with partner. I then went over them.
I provided extra practice worksheets and answer keys for interested students.
Last day to hand in CD 5.1
Wednesday, November 5, 2008 - Blocks 1 and 3
Collected Air Resistance Labs.
Handed out worksheet with friction problems with both static and kinetic coefficients of friction. Students worked on the problems and then I went over them in class.
Described the microscopic causes of friction.
Showed problem with non-horizontal force (force acting upwards at some angle to the horizontal) and showed how this decreased the normal force and thus decreasing the friction force. Related this to blocking in football.
Reviewed topics for test.
Put out extra worksheets for interested students to try at home.
Handed out worksheet with friction problems with both static and kinetic coefficients of friction. Students worked on the problems and then I went over them in class.
Described the microscopic causes of friction.
Showed problem with non-horizontal force (force acting upwards at some angle to the horizontal) and showed how this decreased the normal force and thus decreasing the friction force. Related this to blocking in football.
Reviewed topics for test.
Put out extra worksheets for interested students to try at home.
Tuesday, November 4, 2008 - Blocks 1 and 3
Students worked in pairs to do the Air Resistance Lab. The lab itself did not take too long so students had time to work on the write-up. Lab write-up due on Wednesday.
Monday, November 3, 2008 - Blocks 1 and 3
Handed out packet on solving problems using Newton's laws. The packet showed a worked example focusing on the problem solving strategy. Gave students time to work on the problems, emphasizing the problem solving strategy.
If students did not finish, I asked them to finish for homework and hand in on Tuesday.
If students did not finish, I asked them to finish for homework and hand in on Tuesday.
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