1 physics 1100 – spring 2009 review for exam i friday, february 27 th chapters 1 - 10

1Physics 1100 – Spring 2009

Review for Exam IReview for Exam IFriday, February 27Friday, February 27thth

Chapters 1 - 10Chapters 1 - 10

2Physics 1100 – Spring 2009

3Physics 1100 – Spring 2009

Newton’s 1st lawNewton’s 1st law

If the total “resultant” force acting on an object is zero, then the object will either remain at

rest or it would move along a line with a constant velocity.

4Physics 1100 – Spring 2009

Newtons’ Second LawNewtons’ Second Law

• F = m a

• The acceleration of an object is directly proportional to the net force acting on the object…

• …and inversely proportional to the mass of the object.

5Physics 1100 – Spring 2009

Newton’s Third LawNewton’s Third Law

• Action-Reaction

• Whenever one body exerts a force on a second body…

• …the second body exerts an equal and opposite force on the first body.

6Physics 1100 – Spring 2009

Newton’s Laws in ReviewNewton’s Laws in Review

• 1st

– Law of Inertia

• 2nd

– F = m a

• 3rd

– Action/Reaction

7Physics 1100 – Spring 2009

Linear MotionLinear Motion

• Speed d = v t v = d / t• Velocity (magnitude & direction)• Acceleration a = f / m• Free Fall Velocity v = g t• Free Fall Distance d = ½ g t2

8Physics 1100 – Spring 2009

Chapter 4 - Newton’s Second LawChapter 4 - Newton’s Second Law

• F = m a• Friction• Mass• Weight• Terminal Velocity

9Physics 1100 – Spring 2009

Vector or Scalar?Vector or Scalar?

• Speed………..• Velocity……...• Acceleration..• Time………….• Distance……..• Force…………

scalar

vector

vector

scalar

scalar

vector

10Physics 1100 – Spring 2009

Mass Mass

• the quantity of matter in an object

• the measurement of the inertia

• measured in kilograms (kg)

11Physics 1100 – Spring 2009

WeightWeight• the force upon an object due to gravity

• Weight = Mass Acceleration of gravity

W = mg

• measured in Newtons (N) in the metric system or pounds (lb) in the British system

12Physics 1100 – Spring 2009

When Acceleration Is Zero...When Acceleration Is Zero...

• …we say the object is in Mechanical Equilibrium.

• …the net force is zero.

13Physics 1100 – Spring 2009

• Friction - a force that resists motion

– Static frictional force: when nothing is sliding

– Sliding frictional force: when surfaces are sliding

– Static frictional forces always greater than sliding ones

• Inertia - the resistance of an object to change in its state of motion

Friction

14Physics 1100 – Spring 2009

Free FallFree Fall

15Physics 1100 – Spring 2009

• Momentum - Inertia in motion– momentum = m v

– Impulse = F t = ∆ m v

• Inertia - the resistance of an object to change in its state of motion

Momentum

16Physics 1100 – Spring 2009

Energy definitions Energy definitions

• Potential Energy (due to Earth’s gravity) P.E. = m g h

• Kinetic Energy K.E. = ½ m v2

• Work (units: 1 N * 1 m = 1 joule = .239 calories) W = F d = ∆ Kinetic Energy

• Power (units: 1 joule / second = 1 watt) 1 Kilowatt = 1000 watts and 1 Megawatt = 1M watts 1 HorsePower = 746 Watts

P = W / t

17Physics 1100 – Spring 2009

Momentum and ImpulseMomentum and Impulse

18Physics 1100 – Spring 2009

Momentum & ImpulseMomentum & Impulse

19Physics 1100 – Spring 2009

Vector AdditionVector Addition

20Physics 1100 – Spring 2009

TorqueTorque

• Torque is the product of the force and lever-arm distance, which tends to produce rotation.

• Torque = force lever arm– Examples:

• wrenches

• see-saws

21Physics 1100 – Spring 2009

Rotational InertiaRotational Inertia • An object rotating about an axis tends to remain rotating

unless interfered with by some external influence.

• This influence is called torque.

• Rotation adds stability to linear motion.– Examples:

• spinning football

• bicycle tires

• Frisbee

22Physics 1100 – Spring 2009

• The greater the distance between the bulk of an object's mass and its axis of rotation, the greater the rotational inertia.

• Examples: – Tightrope walker

– Ring and Disk on an Incline

– Metronome

23Physics 1100 – Spring 2009

Centripetal ForceCentripetal Force

• …is applied by some object.• Centripetal means "center seeking".

Centrifugal ForceCentrifugal Force

• …results from a natural tendency.• Centrifugal means "center fleeing".

24Physics 1100 – Spring 2009

Circular MotionCircular Motion

• Linear speed - the distance moved per unit time. Also called simply speed.

• Rotational speed - the number of rotations or revolutions per unit time.

• Rotational speed is often measured in revolutions per minute (RPM).

25Physics 1100 – Spring 2009

Angular MomentumAngular Momentum

• Another conserved quantity is angular momentum, relating to rotational inertia:

• Spinning wheel wants to keep on spinning, stationary wheel wants to keep still (unless acted upon by an external rotational force, or torque)

• Newton’s laws for linear (straight-line) motion have direct analogs in rotational motion

26Physics 1100 – Spring 2009

GravityGravity

• Newton’s Universal Law of Gravitation:

F = GM1M2/r2

27Physics 1100 – Spring 2009

GravityGravity

• Weight • the force due to gravity on an object

• Weight = Mass Acceleration of Gravity

• W = m g

• Weightlessness - a conditions wherein gravitational pull appears to be lacking– Examples:

• Astronauts

• Falling in an Elevator

• Skydiving

• Underwater

28Physics 1100 – Spring 2009

Projectile MotionProjectile Motion

• Break the motion into 2 aspects, “components”– Horizontal

– Vertical

• There is no force acting in the horizontal direction– Horizontal velocity does not change

– Horizontal distance = time in air x horizontal velocity

• There is a force acting in the vertical direction – force of gravity!– Vertical velocity changes the same as if the projectile had been

thrown straight up (or dropped)

– Time in air determined by vertical travel

29Physics 1100 – Spring 2009

ProjectilesProjectiles

30Physics 1100 – Spring 2009

31Physics 1100 – Spring 2009

Projectile ExampleProjectile Example

• The boy on the tower throws a ball 20 meters downrange as shown. What is his pitching speed?

Use the equation for speed as a "guide to thinking.“ v = d/t

d is 20m; but we don't know t… the time the ball takes to go 20m. But while the ball moves horizontally 20m, it falls a vertical distance of 4.9m, which takes 1 second… so t = 1s.

32Physics 1100 – Spring 2009

Equation Sheet

Newton’s Law’s

• If FNet =0, then a =0

• If FNet >0, then FNet = ma

• FAB = - FBA

Linear Displacement• Speed v = d / t• Distance (constant speed) d = v t• Acceleration a = f / m• Velocity (constant a) v = a t• Distance (constant a) d = ½ a t2

• Free-fall acceleration = g = 10 m/s2

Weight• W = mg

Momentum• Momentum (p) = mv• Change in p (p) = Impulse = F t• System with no external force

pinitial = pfinal

Energy and Energy Conservation• E = PE + KE• PE = mgh• KE = ½ mv2

• Work = Fparallel x = E• Power (P) = Energy/time = E/t

Rotational Kinematics• Angular velocity = linear velocity/radius =v/r• v(linear) = r• Torque () = Force x Lever Arm• Rotational Inertia ()• Angular momentum L = • System with no external torque

Linitial = Lfinal

Gravity

• F = GMF = GM11MM22/r/r22

Units• Mass = kg (kilograms)• Distance = m (meters)• Force = kg m/s2 = 1 Newton• 1 Joule (J) = 1 N m• 1 Watt = 1J/s