Honors Physics Semester 1 Review PowerPoint

Distance vs Displacement Distance = magnitude only = 8m Displacement = magnitude and direction = Δx = x 2 – x 1 Δx = x 2 – x 1 = 9m – 1m = +8m

Acceleration When you increase your speed in a car, are you accelerating? When you turn in a car, are you accelerating? When you slow down in a car, are you accelerating? This is called deceleration or negative acceleration or acceleration in the direction opposite of the car’s movement.

Objectives: define distance and calculate speed, and explain what is meant by scalar quantity. Scalar Quantity: Quantity with only a numerical value Distance tells us how far but not in what direction. Time Mass Temperature

Graphical Analysis Zero accelerationPositive acceleration

Kinematics Speed: the rate at which distance is traveled Constant Speed: speed of object does not change Average speed = total distance/total time Units: meters m second s

REVIEW: Motion: change of position Scalar: numbers only Vector: direction Velocity: change of speed in a given direction Acceleration: a change in velocity Therefore, a change in speed or a change in direction

Graphs Position v Time graphs constant velocity Δ v = acceleration

Speed and Velocity There are two types of Velocity: 1. Average Velocity V = ∆d/∆t For example, when a car moved 50 km in 2 hours, the average velocity is 25km/h. 2. Instantaneous Velocity For example, when the speed cameras give you a ticket, they show the car driving at 90 km/h for that instant.

Velocity What is the velocity of this object between 0-4 sec? What is the initial starting position of the object? What is the displacement of this object from 3-4 seconds? What is the object’s final position? Position in Meters

Graphs Assuming the objects motion does not change, what would its position be at t=20s? Time (seconds) Position in Meters

What is happening to the velocity of these two objects? What is happening at t=2s? At t=4s, which object has greater speed?

Graphical Analysis Zero accelerationPositive acceleration

Newton’s First Law of Motion or Law of Inertia: in the absence of an unbalanced force, a body at rest remains at rest, and a body in motion remains in motion with a constant velocity (speed and direction).

Inertia and Newton’s 1 st Law Inertia - tendency of an object to overcome a change in motion Characteristics: more mass = more inertia Mass is the quantitative measure of inertia.

Net Forces

Normal Force When an object is sitting on a level surface then the normal force is always equal and opposite of the weight of the object.

Forces Symbols F app – applied force (push or pull) F g – force of gravity (always toward center of earth or down) F n – normal force (always perpendicular to surface) F f – force of friction (same as surface)

Balanced forces do not change the object’s motion.

FORCES Unbalanced forces result in a change in the object’s motion.

Newton’s First Law of Motion or Law of Inertia: in the absence of an unbalanced force, a body at rest remains at rest, and a body in motion remains in motion with a constant velocity (speed and direction).

Newton’s 3 rd Law of Motion For every force (action), there is an equal and opposite force (reaction).

Free Fall – Force of Gravity ONLY Free Fall: A Particular Acceleration How fast a falling object moves is entirely DIFFERENT from how far it moves. We will treat x and y separately

SI Unit: Newton = kg m/s 2 Force is a vector (magnitude/direction) Like velocity and acceleration, force has a strength AND a direction

FORCE Resultant Force: the total of all forces acting on an object. Force 1 pushes upward with 2 N Force 2 pushes horizontally with 5 N

Net Forces with angles

What is the net force on this object? What is F s ? What is F N ? Pull Force of 20 N at 16° 50kg

Types of Friction Static Friction: Frictional force is sufficient to prevent motion between surfaces.

Static Friction Formula f s ≤ µ s N (static conditions = no movement) µ s coefficient of static friction

Friction (think about ice)

Normal Force Normal means perpendicular. Force that a surface exerts on an object.

Normal Force When an object is sitting on a level surface then the normal force is always equal and opposite of the weight of the object.

Force Formula Acceleration of an object is directly proportional to the net force and inversely proportional to its mass. Acceleration = Force Mass

Momentum and Impulse The concept of impulse and momentum using Newton’s 2nd Law: F = ma a = v f – v i = ΔvF = m Δv t t t Take t to the other side: Impulse-Momentum Theorum = F t = m Δv F(t) is called IMPULSE. It is defined as a force acting through time. Impulse is numerically equal to the Δ of momentum. So a force acting for time on some object gives rise to a change of the object’s momentum.

Is momentum conserved? YES. The momentum lost by one object is gained by the other object. The total amount is constant.

Elastic Collisions Total Kinetic Energy is conserved Follows the Law of Conservation of Momentum K after = K before

Inelastic Collisions Kinetic energy is NOT conserved Change in original shapes Sound and friction – KE lost

Linear Momentum Formula: ρ = m v ρ = momentum m = mass v = velocity SI Units? kg m/s

Law of Conservation of Linear Momentum: "the total momentum of an isolated system of interacting bodies remains constant." OR "Total momentum of an isolated system before collision is always equal to total momentum after collision.“ Correlates to Newton’s 1 st Law of Motion

Radians  Correct SI unit for angular measurements  radius to arc length = radian (The Rad)  1 rad = 360˚/2π = 57.3˚  Calculators: switch to rad when told

Period and Frequency Frequency: number of cycles per unit of time. f = 1/t or s -1 Period: (t) time it takes an object in circular motion to complete one revolution or cycle t = 1/f Frequency and period = inverse relationship Frequency SI: 1/s = Hertz (Hz) Heinrich Rudolf Hertz

Uniform Circular Motion  Needs 3 things  1. Centripetal Force

Uniform Circular Motion  2. Angular Acceleration  3. Constant Speed V= Tangential velocity wants to go in a straight line

Gravitational Field Lines for Two Objects

Kepler’s 3 rd Law of Planetary Motion This Law lets us determine a newly discovered planet’s distance from the Sun.

Kepler’s Laws of Planetary Motion Kepler’s 2 nd Law: (Law of Areas) A line from the Sun to a planet sweeps out equal areas in equal lengths of time.

Escape Velocity What kind of energy must a man-made satellite have to escape Earth’s gravitational pull? What kind of energy must a man-made satellite have to escape Earth’s gravitational pull? Formula for Escape Velocity: Formula for Escape Velocity: Escape speed = escape surface of Earth is about 11km/s or 7mi/s

 Centrifugal is just Inertia – what Law?  Newton’s 1 st : an object in motion wants to stay in that motion and not change speed or direction unless acted upon by an outside force.