The Frontiers of Matter (in 1932) 1 The periodic chart orders the chemical elements according to their properties. It provides clues to the un- derlying atomic structure. The ‘fundamental particles’ of the periodic chart are the atoms/elements themselves. What are the atoms/elements made of? Jerry Gilfoyle Hunting for Quarks 1 / 42
The Frontiers of Matter (in 1932) 2 The periodic chart orders the chemical elements according to their properties. It provides clues to the un- derlying atomic structure. The ‘fundamental particles’ of the periodic chart are the atoms/elements themselves. What are the atoms/elements made of? Protons and neutrons Jerry Gilfoyle Hunting for Quarks 1 / 42
The Frontiers of Matter (in 1932) 3 The periodic chart orders the chemical elements according to their properties. It provides clues to the un- derlying atomic structure. The ‘fundamental particles’ of the periodic chart are the atoms/elements themselves. What are the atoms/elements made of? Protons and neutrons What are the protons and neutrons made of? Jerry Gilfoyle Hunting for Quarks 1 / 42
The Frontiers of Matter (in 1932) 4 The periodic chart orders the chemical elements according to their properties. It provides clues to the un- derlying atomic structure. The ‘fundamental particles’ of the periodic chart are the atoms/elements themselves. What are the atoms/elements made of? Protons and neutrons What are the protons and neutrons made of? Quarks and gluons Jerry Gilfoyle Hunting for Quarks 1 / 42
The Frontiers of Matter (now) 5 The Universe is made of quarks and leptons and the force carriers. The atomic nucleus is made of protons and neutrons bound by the strong force. The quarks are confined inside the protons and neutrons. Protons and neutrons are NOT confined. Jerry Gilfoyle Hunting for Quarks 2 / 42
Setting the Quarks Free 6 Despite quark confinement there is a way to get them out of the proton or neutron. Hit a quark hard enough with something small like an electron and if it is immersed in nuclear matter, the tug of the nearby protons and neutrons cancels some of the forces on the struck quark. We’ll model this struck quark as a particle moving through the nucleus bound to its original partners by a string that exerts a constant force. Does the quark make it out of the nucleus? Scattered electron Struck quark Target quark confined to a proton v Incoming electron b Quark string v o = 3 × 10 8 m / s | a | = 4 × 10 30 m / s 2 R Pb b = 3 . 0 × 10 − 15 m R Pb = 7 . 1 × 10 − 15 m Lead nucleus Jerry Gilfoyle Hunting for Quarks 3 / 42
One-Dimensional Motion 7 position ( x ) time ( t ) Jerry Gilfoyle Hunting for Quarks 4 / 42
One-Dimensional Motion 8 A position ( x ) B time ( t ) Jerry Gilfoyle Hunting for Quarks 5 / 42
One-Dimensional Motion 9 A position ( x ) B Δ t time ( t ) Jerry Gilfoyle Hunting for Quarks 6 / 42
One-Dimensional Motion 10 A position ( x ) B Δ x Δ t time ( t ) Jerry Gilfoyle Hunting for Quarks 7 / 42
One-Dimensional Motion 11 A position ( x ) B Δ x Δ t time ( t ) Jerry Gilfoyle Hunting for Quarks 8 / 42
One-Dimensional Motion 12 A position ( x ) B Δ t time ( t ) Jerry Gilfoyle Hunting for Quarks 9 / 42
One-Dimensional Motion 13 A B position ( x ) Δ t time ( t ) Jerry Gilfoyle Hunting for Quarks 10 / 42
One-Dimensional Motion 14 B A position ( x ) Δ t time ( t ) Jerry Gilfoyle Hunting for Quarks 11 / 42
One-Dimensional Motion 15 B A position ( x ) Δ t time ( t ) Jerry Gilfoyle Hunting for Quarks 12 / 42
One-Dimensional Motion 16 B A position ( x ) Δ t time ( t ) Jerry Gilfoyle Hunting for Quarks 13 / 42
One-Dimensional Motion 17 Tangent line B A position ( x ) Δ t time ( t ) Jerry Gilfoyle Hunting for Quarks 14 / 42
One-Dimensional Motion 18 Tangent line B B B A A A A A B position ( x ) B Letting Δ t → 0 time ( t ) Jerry Gilfoyle Hunting for Quarks 15 / 42
One-Dimensional Motion 19 An elevator in the world’s tallest building, the Burj Dubai in Dubai, United Arab Emirates, is mov- ing and its vertical position is de- scribed by the following equation x ( t ) = A + Bt + Ct 2 where A = 5 . 0 m , B = 2 . 1 m / s , and C = − 4 . 9 m / s 2 . What is the instantaneous velocity at any time t ? What is the average velocity between two times t 0 = 0 . 0 s and t 1 = 1 . 0 s ? Jerry Gilfoyle Hunting for Quarks 16 / 42
Position and Velocity 20 Jerry Gilfoyle Hunting for Quarks 17 / 42
Captain Kirk’s Bad Day 21 The starship Enterprise has lost power and is plunging straight into the heart of a black hole. Its velocity as a function of time is described by v ( t ) = F + Gt where F = 2 . 0 × 10 7 m / s and G = 9 . 0 × 10 10 m / s 2 . What is the instantaneous accelera- tion? Do the velocity and acceleration ver- sus time plots make sense? Jerry Gilfoyle Hunting for Quarks 18 / 42
Catching Up 22 At the instant a traffic light turns green, a ‘car’ starts with a constant acceleration a = 2 . 2 m / s 2 . At the same instant a truck is 5.0 m behind the car and traveling with a constant speed v t = 9 . 5 m / s . How far does the car travel before overtaking the truck? What do the position versus time plots look like for the car and the truck? Jerry Gilfoyle Hunting for Quarks 19 / 42
Catching Up 23 At the instant a traffic light turns green, a ‘car’ starts with a constant acceleration a = 2 . 2 m / s 2 . At the same instant a truck is 5.0 m behind the car and traveling with a constant speed v t = 9 . 5 m / s . How far does the car travel before overtaking the truck? What do the position versus time plots look like for the car and the truck? Position ( x ) Truck Car time ( t ) Jerry Gilfoyle Hunting for Quarks 19 / 42
EEEEKKK!! 24 Two trains, one traveling at 20 m / s and the other at 40 m / s , are headed toward one another along a straight, level track. When they are 950 m apart, each engineer sees the other’s train and instantly applies the brakes. The slow-moving train stops. The brakes decelerate each train at a rate of 1 . 0 m / s 2 . Is there a collision? If so, how long after the brakes are applied? Jerry Gilfoyle Hunting for Quarks 20 / 42
EEEEKKK!! 25 Two trains, one traveling at 20 m / s and the other at 40 m / s , are headed toward one another along a straight, level track. When they are 950 m apart, each engineer sees the other’s train and instantly applies the brakes. The slow-moving train stops. The brakes decelerate each train at a rate of 1 . 0 m / s 2 . Is there a collision? If so, how long after the brakes are applied? Jerry Gilfoyle Hunting for Quarks 20 / 42
Don’t Do This At Home 26 A window washer named Chris Sag- ger is reported to have fallen (as- sume starting from rest) 67 meters from a building where he was work- ing, landed on a car, and lived. Sup- pose the roof of the car was com- pressed 1 . 45 m . Ignoring air resis- tance what is his speed just before hitting the car? Treating his accel- eration as constant, how long did it take him to come to a stop after he made contact with the box? What was his acceleration? Jerry Gilfoyle Hunting for Quarks 21 / 42
Measurement and Uncertainty 27 Average and Standard Deviation True value Number of Measurements Same number of measurements with different standard deviations Same average x Jerry Gilfoyle Hunting for Quarks 22 / 42
Precision versus Accuracy 28 Not precise. Precise, but not accurate. Precise and accurate. Average and Standard Deviation Average and Standard Deviation Average and Standard Deviation True value True value True value Number of Measurements Number of Measurements Number of Measurements x x x Jerry Gilfoyle Hunting for Quarks 23 / 42
Understanding some Statistics 29 Average and Standard Deviation Number of Measurements x Jerry Gilfoyle Hunting for Quarks 24 / 42
σ σ Understanding some Statistics 30 Average and Standard Deviation True value Number of Measurements x Jerry Gilfoyle Hunting for Quarks 25 / 42
σ σ Understanding some Statistics 31 Average and Standard Deviation True value Number of Measurements 68 % of area x Jerry Gilfoyle Hunting for Quarks 26 / 42
Does the quark escape? 32 An electron strikes the quark bound inside a proton that is a constituent of a lead nucleus in the configuration shown in the figure. The quark is near the surface of the nucleus. The collision gives the quark an initial velocity � v o and an acceleration � a as it moves through the nuclear medium. See below for numbers. Does the quark make it out of the nucleus? v o = 3 × 10 8 m / s | a | = 4 × 10 30 m / s 2 Struck quark b = 3 . 0 × 10 − 15 m v R Pb = 7 . 1 × 10 − 15 m 0 b R Pb y Lead nucleus x Jerry Gilfoyle Hunting for Quarks 27 / 42
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