Friday, November 19, 2010
Friday, Dec 10, 2010
Collected RA 6.2 and redo of RA 6.1
Handed out RA 6.3 due tomorrow.
Did several examples using the energy balance equation.
Prepped the Looney Tune Lab for tomorrow.
Wrote energy balance for pushing on block with friction and solved for final velocity. Solved the equation using acceleration to get the same answer.
Showed technique of inserting the coefficient into the KE or PE terms to calculate the new KE or new PE. Very powerful and useful technique. (Ex. What happens to the stopping distance of a car if you double the speed and double the mass?
KE old = 1/2 * m*v^2
KE new = 1/2 (2m) * (2v)^2 = 8 * 1/2 * m * v^2
Handed out problem sheet on energy. Gave students time to work on the problems in class.
Handed out RA 6.3 due tomorrow.
Did several examples using the energy balance equation.
Prepped the Looney Tune Lab for tomorrow.
Wrote energy balance for pushing on block with friction and solved for final velocity. Solved the equation using acceleration to get the same answer.
Showed technique of inserting the coefficient into the KE or PE terms to calculate the new KE or new PE. Very powerful and useful technique. (Ex. What happens to the stopping distance of a car if you double the speed and double the mass?
KE old = 1/2 * m*v^2
KE new = 1/2 (2m) * (2v)^2 = 8 * 1/2 * m * v^2
Handed out problem sheet on energy. Gave students time to work on the problems in class.
Thursday, Dec 9, 2010
Handed out RA 6.2 due tomorrow.
Students did a poor job on RA 6.1 so I had them correct mistakes.
Students did Roller Coaster Lab.
Write-up due on Monday.
Students did a poor job on RA 6.1 so I had them correct mistakes.
Students did Roller Coaster Lab.
Write-up due on Monday.
Wed, Dec 8, 2010
Handed back and went over Momentum Test
Started energy
Feynman's Block example
Types of Energy
Places energy can hide - for this unit, GPE = m g h, KE = 1/2 m v^2, Elastic PE = 1/2 k x^2, work = F * d where F is the component of force in the direction of motion.
Conservation of Energy and Energy Balance Equation.
Did example of lifting a 10 kg mass. First at 120 N for 2 seconds, then at 100 N for 4 seconds and then at 60 N for 1 sec to slow it down. Drew force vs time graph. Showed applied force, weight, and net force. Since net impulse is zero, there is no change in momentum and the block comes to rest. Calculated the work done and showed that it was equal to the change in gravitational potential energy.
Main idea: If you lift an object, the work you do is equal to the increase in gravitational potential energy.
Handed out RA 6.1 due tomorrow.
Prepped Roller Coaster Lab.
Started energy
Feynman's Block example
Types of Energy
Places energy can hide - for this unit, GPE = m g h, KE = 1/2 m v^2, Elastic PE = 1/2 k x^2, work = F * d where F is the component of force in the direction of motion.
Conservation of Energy and Energy Balance Equation.
Did example of lifting a 10 kg mass. First at 120 N for 2 seconds, then at 100 N for 4 seconds and then at 60 N for 1 sec to slow it down. Drew force vs time graph. Showed applied force, weight, and net force. Since net impulse is zero, there is no change in momentum and the block comes to rest. Calculated the work done and showed that it was equal to the change in gravitational potential energy.
Main idea: If you lift an object, the work you do is equal to the increase in gravitational potential energy.
Handed out RA 6.1 due tomorrow.
Prepped Roller Coaster Lab.
Friday, Dec 3, 2010
Went over calculating impulse from Force vs Time graphs.
Showed how to solve problems with 2-D inelastic collisions.
Gave quizzes on
7-block elastic collision
7-block elastic and inelastic collisions with different velocities
quiz on impulse and momentum
2nd quiz on impulse and momentum
Assigned end of chapter questions to look at for next time:
2,5,6,7,10,11,12,13.15.19.22.23.25.26.27.28.29.30.31.32.33.35.38.39
Problems 1-6
Showed how to solve problems with 2-D inelastic collisions.
Gave quizzes on
7-block elastic collision
7-block elastic and inelastic collisions with different velocities
quiz on impulse and momentum
2nd quiz on impulse and momentum
Assigned end of chapter questions to look at for next time:
2,5,6,7,10,11,12,13.15.19.22.23.25.26.27.28.29.30.31.32.33.35.38.39
Problems 1-6
Thursday, Dec 2, 2010
Hand back RA 5.2
Show models of elastic collisions - slingshot effect, supernova
Multi-block elastic collisions
Multi-block inelastic collisions
Demo Ballistic Pendulum
Hand out Momentum and Impulse Problem Sheet
Gave students time to work on problems
Test on Tuesday
Show models of elastic collisions - slingshot effect, supernova
Multi-block elastic collisions
Multi-block inelastic collisions
Demo Ballistic Pendulum
Hand out Momentum and Impulse Problem Sheet
Gave students time to work on problems
Test on Tuesday
Wed, Dec 1, 2010
Handed back RA 5.1 and went over it
Collected Inelastic Collision worksheet
Collected RA 5.2
Reviewed collisions.
Collisions Lab
Bowling ball and golf ball competition.
Collected Inelastic Collision worksheet
Collected RA 5.2
Reviewed collisions.
Collisions Lab
Bowling ball and golf ball competition.
Tuesday, Nov 30, 2010
Collected RA 5.1
Handed out RA 5.2 due tomorrow.
Went around the room and asked what they remembered from last class.
Show parts of video dealing with boxing, railroad cars.
Demo with blowpipes and marshmallows to show that longer cannons impart more impulse (same force, longer time) than short cannons. Actually did this yesterday.
Catching and throwing on frictionless ice both give impulse. Catching and throwing is like bouncing. More impulse if bouncing occurs. But...don't know anything about the force unless you know something about the time.
Skare's demo with happy and sad balls knocking down block.
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.
Showed part of video on Pelton Waterwheel
Intro to conservation of momentum: If no net external force acts on the system, then there is no change in momentum.
Conservation of Momentum has never been shown to fail. It does not apply in cases in which there is an external force (such as gravity for a falling object).
Applied Conservation of Momentum to collisions.
Two basic types of collisions:
1. Elastic (Things bounce)
2. Inelastic (Things stick)
If there is no net external force, momentum is conserved in both types of collisions.
Demos with air track for both types of collisions.
Worked inelastic collision problems on board showing problems solving strategy.
Handed out Inelastic Collisions worksheet. Students worked on it in class and handed it in. Actually ran out of time so had students do it for HW
Handed out CD chpt 5 due for the last time on Monday. It asks for pictures, if you don't draw them then I will return the paper.
Handed out RA 5.2 due tomorrow.
Went around the room and asked what they remembered from last class.
Show parts of video dealing with boxing, railroad cars.
Demo with blowpipes and marshmallows to show that longer cannons impart more impulse (same force, longer time) than short cannons. Actually did this yesterday.
Catching and throwing on frictionless ice both give impulse. Catching and throwing is like bouncing. More impulse if bouncing occurs. But...don't know anything about the force unless you know something about the time.
Skare's demo with happy and sad balls knocking down block.
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.
Showed part of video on Pelton Waterwheel
Intro to conservation of momentum: If no net external force acts on the system, then there is no change in momentum.
Conservation of Momentum has never been shown to fail. It does not apply in cases in which there is an external force (such as gravity for a falling object).
Applied Conservation of Momentum to collisions.
Two basic types of collisions:
1. Elastic (Things bounce)
2. Inelastic (Things stick)
If there is no net external force, momentum is conserved in both types of collisions.
Demos with air track for both types of collisions.
Worked inelastic collision problems on board showing problems solving strategy.
Handed out Inelastic Collisions worksheet. Students worked on it in class and handed it in. Actually ran out of time so had students do it for HW
Handed out CD chpt 5 due for the last time on Monday. It asks for pictures, if you don't draw them then I will return the paper.
Monday, Nov 29, 2010
Go over Newton's 3rd Law test.
Introduction to impulse and momentum lesson
Content Objectives:
Student will be able to
. Define impulse and momentum
. Give the correct units for impulse and momentum
. Calculate impulse and momentum
. State that impulse = change in momentum
. Describe several real-life examples using impulse = change in momentum
. Explain why impulse is greater in bouncing than in sticking
Handed out RA 5.1 due Tuesday
Assigned Quia Quiz 5.1-15 Random - REQUIRED QUIZ - do by Wed and get 100% correct
Also put up full quiz with all questions.
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
Marshmallow blow gun demo.
Introduction to impulse and momentum lesson
Content Objectives:
Student will be able to
. Define impulse and momentum
. Give the correct units for impulse and momentum
. Calculate impulse and momentum
. State that impulse = change in momentum
. Describe several real-life examples using impulse = change in momentum
. Explain why impulse is greater in bouncing than in sticking
Handed out RA 5.1 due Tuesday
Assigned Quia Quiz 5.1-15 Random - REQUIRED QUIZ - do by Wed and get 100% correct
Also put up full quiz with all questions.
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
Marshmallow blow gun demo.
Monday, November 8, 2010
Monday, Nov 22, 2010
Go over end of chapter questions, chapter 4: Ex 17, 18, 19, 20, 24, 25, 26, 30, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 44, 48, 49, Prob 8
Go over any questions on Problem sheets
Review for test
Go over any questions on Problem sheets
Review for test
Friday, Nov 19, 2010
Collect RA 6.1 for last time
Go over HW problems. Make sure students follow the problem solving strategy and don't try to take shortcuts by omitting steps.
Two quizzes on inclined plane problems
Did problems 2 and 4 from worksheet.
Test has been rescheduled for Tuesday
Go over HW problems. Make sure students follow the problem solving strategy and don't try to take shortcuts by omitting steps.
Two quizzes on inclined plane problems
Did problems 2 and 4 from worksheet.
Test has been rescheduled for Tuesday
Thursday, Nov 18, 2010
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.
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.
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
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