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Concept guide for Module 2 part A
Emergency Version

Momentum, energy and angular momentum

NOTE: This is the same concept guide as we have on Webcourses, but it is parked on the Physics Department server.
Concept Pages to study Vocabulary 2 B familiar with Exercises I like. Other/comment
Momentum pp. 97-98
  1. linear momentum (symbol p)
  2. change in momentum (symbol Δp)

p.109: #1-4

Change in momentum, Δp, is the same as Δ(mv). Cf. bottom of p. 97.

Packers photo, Chippewa Herald
Photo: Corey Dellenbach, Shawano Leader/AP
Impulse pp. 97-98
  1. Impulse (symbol set F Δt)
  2. interaction time Δt
 p. 109: 5-11. The "interaction time" is Dr. B's vocabulary, in the context of impulse, for the time interval Δt that a net force acts on an object to speed it up or slow it down. Cf. p. 98, first paragraph for the way the textbook authors describe it!
Conservation of momentum pp. 99-106
  1. isolated system
  2. forces inside system
  3. forces from outside system
pp. 109-110: 14-22 All of these exercises break down into the next two concepts: recoil and collision.
Recoil pp. 99-106
  1. recoil
 p. 110: #14, 15. "Working It Out" on page 100 gives a good example of how recoil works. Momentum of bullet must be equal in size but opposite in direction to the momentum of the rifle.
Collision pp. 101-106
  1. total momentum
  2. sledgehammer example (p. 102)
  3. "locked bumpers"
p. 110: #16-22. All of these exercises are basically "collisions" though not in the sense of two cars bumping as in p. 103! We call them collisions because we are using abstract reasoning. That is, we abstract the essence of the interaction of the runner with the giant skateboard (ex. #16) and see that it is essentially like other "standard" collisions, e.g., two billiard balls (ex. #17).
Miscellaneous Ch. 6
  1. net force
  2. acceleration
  3. momentum
pp. 109-110: #12, 13. Generic force-accleration-momentum exercises here are also worth looking into.

Be on the alert for new study tools, blurb sheets etc., TBA.

Kinetic energy

pp. 112-115

  1. kinetic energy (symbol KE)
  2. conservation of kinetic energy
  3. Joule
  4. elastic collision
  5. inelastic collision

p.132: #1-4

If you can work out exercises 3 and 4, you are squared away for this concept.

Also, I really like the math blurb on p. 115, "Working It Out - Conservation of Kinetic Energy."

Work

 pp. 115-118
  1. Work (symbol W)
  2. "distance through which force acts" (symbols: d, Δx)
  3. "forces that do no work"
p. 132: #7, 9, 11, 12

The work formula, W = F Δx, is appropriate for exercises 7 and 9.

Potential energy

 pp. 118-119
  1. potential energy
  2. gravitational potential energy (symbol GPE)
  3. height
  4. zero-level, zero-point, zero-value
pp. 132-133: #14, 15

"The amount of gravitational potential energy an object has is a relative quantity. Its value depends on how we define the height - that is, what height we take as the zero value." (p. 119)

Total mechanical energy

 pp. 119-126
  1. mechanical energy (symbol ME)
    In Dr. B parlance: total mechanical energy (symbol E)
  2. conservation of mechanical energy
    In Dr. B parlance: conservation of energy
 p. 133: #17

The roller coaster discussion is excellent. The game Roller Coaster Typhoon avoids the problem of Fig. 7-11 by having a chain pull the cars to the top of the tallest hill. Exercise 19 is about roller coasters.

Exercise 18 is a good "table" problem.

Power

 pp. 127-128
  1. Power
  2. Watt
  3. kiloWatt hour
p. 133: #23

Basic information for understanding your light bill!

SYMBOLS! --

There are three dynamical quantities that use the symbol W.

  1. Weight force
    W = mg
  2. Work
    W = F Δx
  3. unit for measuring power
    Watt
    1W = 1 Joule/sec
Be careful!

 -- You can usually deduce the correct W concept from the context, by careful reading.
Practical physics kinetic energy transfer
Kinetic energy ready, as soon as the cart is released. This is equivalent to saying that the spring contains potential energy!
(Thanks to PracticalPhysics.org website for this clear, nice diagram!)
Rotation pp. 135, 138
  1. rotation
  2. rotational speed
  3. rotational velocity
  4. rotational acceleration
  5. rotational inertia
p. 150: Exercises 1-6 Basic terminology
Torques pp. 135-141
  1. torque
  2. axis
  3. center of mass
  4. stable equilibrium
  5. unstable equilibrium
p. 150: Exercises 7-14. Diagrams of forces, axes and torques are critical. E.g., Figure 8-3.
Rotational Kinetic Energy p. 142
  1. rotational kinetic energy
  2. linear speed (as opposed to rotational speed)
-- The formula for rotational K.E., ½Iω2, is amazingly similar to the formula for regular K.E., ½mv2. It is one of the facts of Nature that really spurred my interest in physics as an undergraduate.
Angular momentum p. 142-145
  1. angular momentum
  2. linear momentum (as opposed to angular momentum)
  3. conservation of angular momentum
p. 151: Exercises 15, 16, 17*, 18*

Angular momentum is an unusual vector. The conservation law for this vector is powerful.

The exercises with an asterisk are BRAIN BURNERS!!!!!!!!