Honors Physics Semester 1 Review Power Point Distance

Honors Physics Semester 1 Review Power. Point

Distance vs Displacement 0 1 2 3 4 5 6 7 8 9 Distance = magnitude only = 8 m Displacement = magnitude and direction = Δx = x 2 – x 1 = 9 m – 1 m = +8 m

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 acceleration Positive acceleration

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

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 Δv = 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 25 km/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.

Position in Meters 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?

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

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

Graphical Analysis Zero acceleration Positive 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 l 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 Fapp – applied force (push or pull) Fg – force of gravity (always toward center of earth or down) Fn – normal force (always perpendicular to surface) Ff – 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

Net Forces with angles What is the net force on this object? Pull Force of 20 N at 16° 50 kg What is Fs? What is FN?

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

Static Friction Formula n fs ≤ µs. N (static conditions = no movement) n µscoefficient 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 2 nd Law: • F = ma a = vf – vi = Δv F = 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 • Kafter = Kbefore

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: 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

rd Kepler’s 3 Law of Planetary Motion l 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 l What kind of energy must a man-made satellite have to escape Earth’s gravitational pull? l Formula for Escape Velocity: Escape speed = escape surface of Earth is about 11 km/s or 7 mi/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.