CHAPTER 5 NOTESCHAPTER 5 NOTES

KONICHEKKONICHEK

I. Dynamics- why objects move the way I. Dynamics- why objects move the way they do, they do,

A.. kinematics studied how objects moveA.. kinematics studied how objects move

1. Isaac Newton- First to study the 1. Isaac Newton- First to study the causes of accelerationscauses of accelerations

a. summarized them in 3 laws of a. summarized them in 3 laws of motionmotion

Welcome to the concept of Welcome to the concept of universal forcesuniversal forces

II.Force- a push or pull A. 4 types of forces 1. Gravitational- the force of attraction

between all objects a. weakest of the 4 forces b. carried by the graviton 1. only become significant with

large amounts of mass.

2. Electromagnetic forces- the forces caused by the charges between particles-

a. carried by the photon b. produced by the motion of charged

particles. The magnetic field and the electric field vibrate at 90 to each other.

1. act as a single force- electromagnetic force

►3. Strong nuclear- this is the force 3. Strong nuclear- this is the force which hold the nucleus togetherwhich hold the nucleus together

► a. strongest of the 4 forces- 100 a. strongest of the 4 forces- 100 times strongertimes stronger

► b. acts for very short distances b. acts for very short distances ► 4. Weak force-a form of EM forces4. Weak force-a form of EM forces► a. decay of some types of nucleia. decay of some types of nuclei

B. Grand unified theory- at some B. Grand unified theory- at some point in time all 4 forces acted as a point in time all 4 forces acted as a single unified forcesingle unified force

1. Planck time 101. Planck time 10-43-43 this is the this is the conditions which may explain the big conditions which may explain the big bangbang

a, all know physics breakdown a, all know physics breakdown at this pointat this point

Isaac and his 3 laws

III.Newtons Laws of Motion( Galileo based)III.Newtons Laws of Motion( Galileo based) A. First law- an Object with no force acting on it moves with a A. First law- an Object with no force acting on it moves with a

constant velocity.constant velocity. 1. unbalanced forces- This is a force which causes motion to 1. unbalanced forces- This is a force which causes motion to

occur.occur. 2. Balanced forces- equilibrium- the sum of all the forces 2. Balanced forces- equilibrium- the sum of all the forces

acting on an object is zeroacting on an object is zero 3. Must assign signs to show the direction of the force3. Must assign signs to show the direction of the force a. positive forces to the righta. positive forces to the right b. negative forces to the leftb. negative forces to the left 4. To find the net force it is the summation of all the forces 4. To find the net force it is the summation of all the forces

acting on the object.acting on the object. a. if the net force is zero the velocity is zero and no a. if the net force is zero the velocity is zero and no

motion results.motion results. 5. Expanding the first law- an Object with no net force acting 5. Expanding the first law- an Object with no net force acting

on it remains at rest or moves with a constant velocity in a on it remains at rest or moves with a constant velocity in a straight line.straight line.

EXAMPLE OF FIRST LAWEXAMPLE OF FIRST LAW

POOR LITTLE TEST TUBEPOOR LITTLE TEST TUBE

Mr. Konichek testing the First Law.Mr. Konichek testing the First Law.wow man!wow man!

B. Second Law- The acceleration of a body is directly proportional to the net force and inversely proportional to its mass 1. F=ma 2. as force increases acceleration must increase 3. as mass increases and force is constant the acceleration must decrease 4. The net force on an object causes an acceleration 5. unit for force- 1 Kgm/s2 = 1 Newton( N)

HEY- 2ND LAW EXAMPLES

C. Sample problems 1. what is the net force of an object

accelerating at 5m/s2 and has a mass of 500Kg?

2. What is the acceleration of a 3000Kg truck which has a force of 8000N applied to it?

D. Finding force when acceleration D. Finding force when acceleration must be calculated, given the final must be calculated, given the final velocity, and distance, velocity, and distance,

1.initial velocity is zero( Impulse 1.initial velocity is zero( Impulse force)force)

a. Use Va. Use Vff22= V= Vii

22+ 2ad, solve for a:+ 2ad, solve for a: a= Va= Vff

22-V-Vii22/ 2d/ 2d

substitute into F=Masubstitute into F=Ma F= M(VF= M(Vff

22 –V–Vii

22)/2d )/2d

PRACTICE, PRACTICEPRACTICE, PRACTICE

1. 1. exampleexample - a cannon ball with a mass of - a cannon ball with a mass of 60Kg is fired from a cannon at a velocity of 60Kg is fired from a cannon at a velocity of 70m/s. the cannon is 2.5m long, assuming 70m/s. the cannon is 2.5m long, assuming the force and acceleration are constant. the force and acceleration are constant. What would be the force on the cannon What would be the force on the cannon ball while it is in the barrel of the cannon?ball while it is in the barrel of the cannon?

ASSIGNMENT- PAGE 92 1-4ASSIGNMENT- PAGE 92 1-4

►E. Third Law of Motion- For each action E. Third Law of Motion- For each action force there is an opposite and equal force there is an opposite and equal reaction force.reaction force.

► 1. walking, rocket blasting off.1. walking, rocket blasting off.► 2. only the force exerted on the 2. only the force exerted on the

object will cause an acceleration.object will cause an acceleration.

Kick of a gun

• IV. Using Newton's Laws• A. Mass and weight-• 1. mass- the quantity of matter• 2. weight- The gravitational force

exerted by a large body• a. w=mg• b. On earth. 1kg9.8m/s2= 1

Newton

B. Types of massesB. Types of masses 1. Inertial mass- The ratio of the net force 1. Inertial mass- The ratio of the net force exerted on an object and it’s accelerationexerted on an object and it’s acceleration

a. Ma. Mii= F/a= F/a

2. Comparison method- Compare the mass 2. Comparison method- Compare the mass of unknown quantity to one of known quantity on of unknown quantity to one of known quantity on a balance.a balance. a. When the pans balance the masses a. When the pans balance the masses are equal. are equal.

C. Friction- This is the force between two surfaces C. Friction- This is the force between two surfaces which are in contact with each other.which are in contact with each other.

1. Causes- all surfaces are rough, when 1. Causes- all surfaces are rough, when they rub against each other there is a weak they rub against each other there is a weak electromagnetic bond set up between the electromagnetic bond set up between the surfacessurfaces

2. Static Friction- This is the force which 2. Static Friction- This is the force which opposes the start of motionopposes the start of motion

a. Have the maximum values of a. Have the maximum values of frictional forcesfrictional forces

b. Must overcome the static friction b. Must overcome the static friction when moving something.when moving something.

3. Sliding friction-The force between sliding surfaces 3. Sliding friction-The force between sliding surfaces a. Less that the static frictiona. Less that the static friction 4. Force of friction4. Force of friction( assignment P 99- 9 and 10)( assignment P 99- 9 and 10) a. depends upon the force pushing the surfaces a. depends upon the force pushing the surfaces

together and the nature of the surfaces in contact.together and the nature of the surfaces in contact. 1. F1. Fff= MuFn (F== MuFn (F=μμFFnn)) a. a. μμ((Mu)= coefficient of frictionMu)= coefficient of friction b. Fb. Fnn= Normal force- perpendicular to the = Normal force- perpendicular to the

line of motionline of motion 1. It’s the sum of all the downward 1. It’s the sum of all the downward

forces on the object.forces on the object. b. We will assume the coefficient of sliding b. We will assume the coefficient of sliding

friction is independent of the surface area and friction is independent of the surface area and velocity.velocity.

► D. The net force causes accelerationD. The net force causes acceleration► 1. The acceleration of an object is the 1. The acceleration of an object is the

result of the net force acting on the object.result of the net force acting on the object.► 2. The net force is the vector sum of 2. The net force is the vector sum of

the applied force and the frictional forcethe applied force and the frictional force► a) Fa) Fnetnet= F= Fappliedapplied + F + Ffrictionfriction

► b) Fb) Fnetnet=F=Fgroundground+ weight+ weight

► c) throwing up the stone Fc) throwing up the stone Fnn= = FFobjectobject+ Weight + Weight

FREE FALL- FREE FALL-

E. The fall of bodies in airE. The fall of bodies in air 1. In a vacuum all objects accelerate at the 1. In a vacuum all objects accelerate at the

same ratesame rate 2. In the atmosphere objects will fall at 2. In the atmosphere objects will fall at

different rates because of air resistancedifferent rates because of air resistance a. drag- The force of the atmosphere a. drag- The force of the atmosphere

against a moving object- form of frictionagainst a moving object- form of friction 3. depends on:3. depends on: a. size, shape, the air density, and the a. size, shape, the air density, and the

speed of motion.speed of motion.

F. Universal Gravitation- all objects with F. Universal Gravitation- all objects with mass attracts themselves directly mass attracts themselves directly proportional to the masses and inversely proportional to the masses and inversely proportional to the square of the distance.proportional to the square of the distance.

1) F= Gm1) F= Gm11mm11/R/R22

2) G=6.67x102) G=6.67x10-11-11NmNm22/kg/kg22

4. Falling objects gravity is pulling harder than the drag a. as the velocity of the object increases the drag increases until the drag force equals the pull of gravity... net force is zero 1. the object stops accelerating... terminal velocity 2. a falling parachutist spread eagle falls about 60m/s 3. with the chute open 5m/s.PRACTICE PROBLEMS ASSIGNMENT PAGE 105 :1, P106 :4,6,8,9,10, 12,15,p 107- 22 ,24