energy introduction section 0 lecture 1 slide 1 lecture 13 slide 1 introduction to modern physics...
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Energy
Introduction Section 0 Lecture 1 Slide 1
Lecture 13 Slide 1
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 13
Energy
Energy
Introduction Section 0 Lecture 1 Slide 2
Lecture 13 Slide 2
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
PHYSICS OF TECHNOLOGY Spring 2009 Assignment Sheet
*Homework Handout
Date Day Lecture Chapter Homework Due Jan 5 6 7 9
M T W F*
Class Admin: Intro.Physics Phenomena Problem solving and math Units, Scalars, Vectors, Speed and Velocity
1 App. B, C 1 2
-
Jan 12 14 16
M W F*
Acceleration Free Falling Objects Projectile Motion
2 3 3
1
Jan 19 21 23
M W F*
Martin Luther King Newton’s Laws Mass and Weight
No Class 4 4
2
Jan 26 28 29 30
M W Th F
Motion with Friction Review Test 1 Circular Motion
4 1-4 1-4 5
3
Feb 2 4 6
M W F*
Planetary Motion and Gravity Energy Harmonic Motion
5 6 6
4
Feb 9 11 13
M W F*
Momentum Impulse and Collisions Rotational Motion
7 7 8
5
Feb 16 17 18 19 20
M Tu W H F*
Presidents Day Angular Momentum (Virtual Monday) Review Test 2 Static Fluids, Pressure
No Class 8 5-8 5-8 9
-
Feb 23 25 27
M W F*
Flotation Fluids in Motion Temperature and Heat
9 9 10
6
Mar 2 4 6
M W F*
First Law of Thermodynamics Heat flow and Greenhouse Effect Climate Change
10 10 -
7
Mar 9-13 M-F Spring Break No Classes Mar 16 18 20
M W F*
Heat Engines Power and Refrigeration Electric Charge
11 11 12
8
Mar 23 25 26 27
M W H F*
Electric Fields and Electric Potential Review Test 3 Electric Circuits
12 13 9-12 13
-
Mar 30 Apr 1 3
M W F
Magnetic Force Review Electromagnets Motors and Generators
14 9-12 14
9
Apr 6 8 10
M W F*
Making Waves Sound Waves E-M Waves, Light and Color
15 15 16
10
Apr 13 15 17
M W F*
Mirrors and Reflections Refraction and Lenses Telescopes and Microscopes
17 17 17
11
Apr 20 22 24
M W F
Review Seeing Atoms The really BIG & the really small
1-17 18 (not on test) 21 (not on test)
No test week 12
May 1 F Final Exam: 09:30-11:20am
Energy
Introduction Section 0 Lecture 1 Slide 3
Lecture 13 Slide 3
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 13
Energy
Introduction
Energy
Introduction Section 0 Lecture 1 Slide 4
Lecture 13 Slide 4
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Dennison’s Law of minimum effort:
MAKE IT SIMPLE STUPID!!!
Einstein on the Theory of General Relativity: “Everything should be made as simple as possible, but not simpler. ... “
Energy
Introduction Section 0 Lecture 1 Slide 5
Lecture 13 Slide 5
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
... Is there some sort of
conservation law that is related to
Newton’s Laws of motion…
Can we build on what we’ve learned to make our life easier…
Energy
Introduction Section 0 Lecture 1 Slide 6
Lecture 13 Slide 6
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Describing Motion and Interactions
Position—where you are in space (L or meter)
Velocity—how fast position is changing with time (LT-1 or m/s)
Acceleration—how fast velocity is changing with time (LT-2 or m/s2)
Force— what is required to change to motion of a body (MLT-2 or kg-m/s2)
In this chapter we will develop on of the most useful concepts in science…ENERGY…and learn what it means to conserve energy.
Energy
Introduction Section 0 Lecture 1 Slide 7
Lecture 13 Slide 7
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Newton’s Laws in Review
• 1st Law —a special case of the 2nd Law for statics, with a=0 or Fnet=0 • An objects velocity remains unchanged, unless
a force acts on the object.
• 2nd Law (and 1st Law)—How motion of a object is effected by a force.– The acceleration of an object is directly
proportional to the magnitude of the imposed force and inversely proportional to the mass of the object. The acceleration is the same direction as that of the imposed force.
• 3rd Law —Forces come from interactions with other objects.• For every action (force), there is an equal but
opposite reaction (force).
F ma
units : 1 newton = 1 N = 1 kgm s2
Energy
Introduction Section 0 Lecture 1 Slide 8
Lecture 13 Slide 8
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
What can apply to all these sorts of problems…
Forces are acting in each case, but force is not conserved really.
F||
Energy
Introduction Section 0 Lecture 1 Slide 9
Lecture 13 Slide 9
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 13
Energy
Work and Energy
Energy
Introduction Section 0 Lecture 1 Slide 10
Lecture 13 Slide 10
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
• Work is equal to the force applied times the distance moved.– Work = Force x Distance: W = F d– Work output = Work input
• units: 1 joule (J) = 1 Nm = 1 kg m2 / s2 [ML2T-2]
Defining Work
Energy
Introduction Section 0 Lecture 1 Slide 11
Lecture 13 Slide 11
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
• Only forces parallel to the motion do work.• Power is the rate of doing work
– Power = Work divided by Time: P = W / t
units: 1 watt (W) = 1 J / s = 1 kg m2 / s3 [ML2T-3]
Work and Power
Energy
Introduction Section 0 Lecture 1 Slide 12
Lecture 13 Slide 12
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
A string is used to pull a wooden block across the floor without accelerating the block. The string makes an angle to the horizontal. Does the force applied via the string do work on the
block?
a) Yes, the force F does work.
b) No, the force F does no work.
c) Only part of the force F does work.
d) You can’t tell from this diagram.
Only the part of the force that is parallel to the distance moved does work on the block. This is the horizontal part of the force F.
Energy
Introduction Section 0 Lecture 1 Slide 13
Lecture 13 Slide 13
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
If there is a frictional force opposing the motion of the block, does this frictional force do work
on the block?
a) Yes, the frictional force does work.
b) No, the frictional force does no work.
c) Only part of the frictional force does work.
d) You can’t tell from this diagram.
Since the frictional force is antiparallel to the distance moved, it does
negative work on the block.
Energy
Introduction Section 0 Lecture 1 Slide 14
Lecture 13 Slide 14
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Does the normal force of the floor pushing upward on the block do any work?
a) Yes, the normal force does work.
b) No, the normal force does no work.
c) Only part of the normal force does work.
d) You can’t tell from this diagram.
Since the normal force is perpendicular to the distance moved, it does no work on the block.
Energy
Introduction Section 0 Lecture 1 Slide 15
Lecture 13 Slide 15
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
A force of 50 N is used to drag a crate 4 m across a floor. The force is directed at an angle upward from the crate as shown.
What is the work done by the horizontal component of the force?
a) 120 Jb) 160 Jc) 200 Jd) 280 Je) 0 J
The horizontal component of force is 40 N and is in the direction of motion:
W = F · d = (40 N) · (4 m) = 160 J.
Energy
Introduction Section 0 Lecture 1 Slide 16
Lecture 13 Slide 16
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
What is the work done by the vertical component of the force?
a) 120 Jb) 160 Jc) 200 Jd) 280 Je) 0 J
The vertical component of force is 30 N but isn’t in the direction of motion:
W = F · d = (30 N) · (0 m) = 0 J.
Energy
Introduction Section 0 Lecture 1 Slide 17
Lecture 13 Slide 17
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
What is the total work done by the 50-N force?
a) 120 Jb) 160 Jc) 200 Jd) 280 Je) 0 J
Only the component of force in the direction of motion
does work: W = F · d
= (40 N) · (4 m) = 160 J.
Energy
Introduction Section 0 Lecture 1 Slide 18
Lecture 13 Slide 18
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
PHYS 1800
Lecture 13
Energy
Energy and Simple Machines
Energy
Introduction Section 0 Lecture 1 Slide 19
Lecture 13 Slide 19
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Simple Machines, Work, and Power
• A simple machine multiplies the effect of an applied force.– For example, a lever :
• A small force applied to one end delivers a large force to the rock.• The small force acting through a large distance moves the rock a small distance.
F2 d2 = F1 d1
Energy
Introduction Section 0 Lecture 1 Slide 20
Lecture 13 Slide 20
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Simple Machines, Work, and Power
• A simple machine multiplies the effect of an applied force.– For example, a pulley :
• A small tension applied to one end delivers twice as much tension to lift the box.• The small tension acting through a large distance moves the box a small distance.
Energy
Introduction Section 0 Lecture 1 Slide 21
Lecture 13 Slide 21
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
• The mechanical advantage of a simple machine is the ratio of the output force to the input force.– For the pulley example, the mechanical advantage is 2.
• Work is equal to the force applied times the distance moved.– Work = Force x Distance: W = F d
– Work output = Work input• units: 1 joule (J) = 1 Nm= 1 kg m2 / s2 [ML2T-2]
Mechanical Advantage and Simple Machines
Energy
Introduction Section 0 Lecture 1 Slide 22
Lecture 13 Slide 22
INTRODUCTION TO Modern Physics PHYX 2710
Fall 2004
Physics of Technology—PHYS 1800
Spring 2009
Physics of Technology
Next Lab/Demo: Energy & OscillationsCollisions and MomentumThursday 1:30-2:45
ESLC 53 Ch 6
Next Class: Friday 10:30-11:20BUS 318 roomReview Ch 6