Learning Objectives

• Test 2 this week! 
• Ignoble Prize in Rheology
• Launch of Europe Clipper

This weeks test focused on chapter 4 (forces and Newtons laws) and the first part of chapter 5 (friction as a force)

After the test, we discussed the launch of the Europe Clipper satellite along with the stunning ‘catch’ of the SpaceX booster rocket. 

Learning Objectives

Monday was a review of last week’s test. Major point was that every question on the test was one we had seen during class discussion, or was an assigned HW problem or was a solved example from the text book.

Centripetal Forces are reviewed along with the concepts of Period of Motion and Frequency of rotation

New Assignments this week:

• Rocks over your head_fall24

See examples of student notes from this week.

• student notes_10.30a 
• student notes_10.30b
• student notes_10.30c
• student notes_10.30.d

This week circles back to centripetal motion both in general (centripetal forces and acceleration) and with regard to the ‘source of the force’, which can vary from one situation to the next. Of special interest this week, was the case of objects traveling in a vertical plane, being swung by a rope. The example of slowing the rotational velocity down until the rope goes ‘slack’ at the top (Tension just goes to zero) results in the observation that the Force of Gravity is the only force acting on the mass and therefor, must be the Force causing the Centripetal Acceleration.

Learning Objectives

This week married the discussion of centripetal forces in a vertical plane with the concepts of conservation (and transformation) of energy. Specifically, we examined Work and how the motion must be parallel to the forces, Gravitational Potential Energy and Kinetic Energy.

New Assignments: 

• Read sections  7.1 and 7.2 in the On-line text (pages 299-309) Work, Kinetic Energy and the Work Energy theorem.
• Do odd-numbered problems 1-15 on pages 345-346
• solutions_probs 7.1_7.2_Nov01
• Student notes from this week
• notes_banked curves
• notes_banked curves (2)
• notes_rock over head corrections with energy

Demo problem: Work.. A person carries a block up a ramp to a height H, and then allows the block to slide back down (with friction). How much work does the person do, does friction do, and what is the speed of the block at the bottom of the ramp, (and how much heat is produced?).

Discussion: Banked turns and identifying the angle of the bank to keep the car on the road without friction.

Discussion: Reconsidering the ‘rock over your head’ lab which takes into consideration the change in energy from the top of the path to the bottom.

Demo Problem: At what height H, must a block be released so that if it slides down a ramp with a ‘loop’ at the bottom (or radius R), it will stay in contact with the track.

Learning Objectives

New Assignments: 

• Read sections  7.1 and 7.2 in the On-line text (pages 299-309) Work, Kinetic Energy and the Work Energy theorem.
• Do odd-numbered problems 1-15 on pages 345-346 
  • chpt 7 homework solutions
• Meteor Launcher! Students determined the energy stored in a compressed spring and then used that value to predict the launch height of a meteor (a rock? a nut? something small).. when the compressed spring is released. To hand in: A short summary of the physics in action, a data table showing the compression as a function of applied force, a graph showing the slope of the function (the spring constant), a section identifying the available energy when the spring is compressed and a prediction showing how high the projectile ought to attain upon launch.

Video: History of Car Crashes (history channel)

Discussion: Energy stored in a compressed spring.. with a review of work as a concept, and how the area under the curve of force vs distance represents the total work done and the energy now stored in compressing a spring. 

Demo problem: A person weighing 62 kg is about to jump off of a bridge with a Bungee Rope attached. The rope is 12 meters long. As the jumper falls, she drops a total distance of 30 meters below the bridge before she finally stops. Questions include: Where does she experience the maximum force and what is the value? Where does she experience the maximum acceleration and what is it? You tube Video: A person in a wheel chair enjoys bungee jumping! 

Learning Objectives

• Potential Energy stored in a ‘captured’ Spring and how to predict height of a projectile. 
• Gravitational Potential Energy of a system in ‘absolute’ terms.

New Assignments: 

• No new assignments this week. Just time to work on the Spring lab. 

This week continued with the Meteor Launch Lab, characterizing the spring, launching the mass and comparing the outcomes.

Engineering notes: mass of plastic piston = 12 grams.. Mass of Spring is 3 grams (negligible).

Discussion: Gravitational Potential Energy relative to infinity. Earlier in the unit, we discussed Gravitational Potential Energy PE (grav) = mgh. This is the correct equation to use if the question is; ‘how much work to lift a mass, or how fast are you falling after you’ve dropped a certain height. The more formal view of Gravitational Potential however, considers a mass (such as a planet) at some greater distance away from Earth. The basic structure of the argument however, begins with the idea that, at a great distance away (infinity?).. the Potential Energy MUST be zero.. (since the effect of the Force of Gravity is essentially zero at that distance). The discussion then follows the logic presented here, in the Wikipedia page for Gravitational Potential Energy.

Movie Moon (1st half) . Science fiction. (good thing for rainy day right before Thanksgiving break!). 

Learning Objectives

• Linear Momentum and conservation of Momentum

New Assignments: 

• conservation of momentum_fall2024
• Chapter 8 HW set. (starting on page 367)
  • 5, 7, 12, 15, 17, 18, 23, 24, 32, 26, 37.
  • chpt 8 problem solutions 5, 7, 12..

This week is all about momentum. Newtons Cradle demonstrates the phenomena, but the fun is when we crash cars into each other. The lab activity is simply to collide two cars of differing weights into each other, capture the velocity and force data and then to show using graphs that momentum is conserved throughout the collision.

Learning Objectives

• • Linear Momentum and conservation of Momentum
  • final review guide_fall24
  • Solutions to final review guide_fall 2024

New Assignments: 

• conservation of momentum_fall2024
• Chapter 8 HW set. (starting on page 367)
  • 5, 7, 12, 15, 17, 18, 23, 24, 32, 26, 37.
  • chpt 8 problem solutions 5, 7, 12..

This week focused on combining concepts of conservation of energy with conservation of mass.. One interesting problem is the classic “ballistic pendulum problem’ in which a bullet is shot into a suspended block of wood in order to determine the velocity of the bullet.. An entertaining version of this problem is presented here; in this Episode of the Idahoan. .. click the link at right to see an example of Clark’s notes on the problem we solved in class: Clark solves ballistic pendulum problem

Problems Clark reviewed as a class discussion include:

• Problem 8: A car crashes into a tree. Determine the force on the passenger (note: we reviewed this crash test video to make the problem more realistic)
• Problem 10: A boxer hits his opponent with a 1000 Newton blow
• Problem 13: Car runs into a bridge
• Problem 24: two clay masses collide.
• Solutions to demo problems solved in class 8, 10, 13, 24.