PHSYICS

PHSYICSIs a branch of science that deals with the properties, behavior and interaction between matter and energy

Subdivisions of Physics• Classical Mechanics: study of motions based on

Newton’s laws of mechanics• Thermodynamics & Statistical Mechanics: study of

energy conversion involving heat and other forms of energy

• Electromagnetism: interaction of electricity and magnetism, affecting presence/motion of particles

• Relativity: relationship of electromagnetism and mechanics

• Quantum Mechanics: atomic and subatomic systems and their interaction w/ radiation

Measurements How far? How large? How much?

BASIC QUANTITIESLength: locates position of a point in spaceTime: succession of eventsMass: amount of matter in a body

DERIVED QUANTITIES• Volume: amount of space an object takes up

EXAMPLE:What is the volume of a cylinder which has

a diameter of 6 cm and a height of 5 cm?

Formula: V = ∏r2h

Answer: 45 ∏ cm3

• Density: mass of an object per unit volume

EXAMPLEWhat is the density of a 40 ft x 25 ft x 10 ft rectangular prism if it has a mass of 50000 grams?

D = mass/volume

Answer: 5 g/ft3

UNITS OF MEASUREMENT

NAME LENGTH TIME MASS FORCESI Units Meter

(m)Second

(s) Kilogram

(kg)Newton

(N)US

CustomaryFoot (ft) Second

(s)Slug

(lb s2/ft)Pound

(lb)

Conversion of UnitsLENGTH TIME MASS

1 m = 1000 mm1 cm = 10 mm1 m = 100 cm

1 ft = 12 inches1 ft = 0.3048 m

1 inch = 25.4 mm1 mi = 5280 ft

1 min = 60 s1 hr = 60 min1 hr = 3600 s

1 yr = 365 days1 day = 24 hrs

1 kg = 1000 g1 kg = 2.2 lbs

How many mililiters are there in 3.45 L?

Answer: 3450 ml

Try these: 20 seconds = ? hours

10 m/s = ? km/h10 cm3 = ? m3

SIGNIFICANT DIGITS

• Nonzero digits are always significant.• All final zeroes after decimal points are

significant.• Zeroes between two other significant

digits are always significant.• Zeroes used solely for spacing decimal

points are not significant.

SCALARSQuantities described by magnitude alone.

i.e. Length, mass, time, speed, energy, temperature, etc.

VECTORSQuantities described by both magnitude and direction.

i.e. Position, force, displacement, velocity, acceleration, torque, momentum ,etc.

Sense and Directionof vectors can be represented in two ways.

A. Four primary directions

Sense and Directionof vectors can be represented in two ways.

B. Cartesian Plane

MECHANICSBRANCH OF PHYSICS CONCERNING THE MOTIONS OF OBJECTS AND THEIR

RESPONSE TO FORCES.

• DISTANCE: scalar; how much ground an object can cover during its motion

• DISPLACEMENT: vector; how far out of place an object is

Displacement = final position – initial position

• SPEED: scalar; how fast an object is moving

• VELOCITY: vector; rate at which an object changes its position

Average speed = distance travelled/elapsed time

(s=d/t)

Average velocity = ∆ in position/elapsed time

(v=∆d/ ∆t)

• Acceleration: vector; change in velocity over a time interval

a. Positive direction of motion: accelerationb. Negative direction: deceleration

A = (final velocity – initial velocity)/ elapsed time

A = ∆V/ ∆T

What is the average speed of a car that travels 330 km in 11 hours?

s = d/t = 330 km/11hrs = 30 km/hr

A cart accelerates from 88 m/s to 121 m/s in 11 s. What is its acceleration?A = ∆v/ ∆t = (121-88)/11 = 3 m/s2

Uniformly Accelerated Motion(UAM)

•Vf = Vi + at

•D = Vit + 1/2at2

•Vf2 = Vi

2 + 2ad

An automobile is moving at 5 m/s and accelerates at 0.5 m/s2.

What is the velocity after 20 s? What is the distance travelled

by the car?

• FREE FALL – uniformly accelerated motion under the sole influence of gravity.

A = 9.8 m/s2 downward

Downward gravitational acceleration is indicated by making acceleration

negative.

NEWTON’S LAWS OF MOTION

• Law of Inertia- an object at rest will stay at rest, and an object in

motion will stay in motion, unless it is compelled to change that state by external forces.

Inertia: property of matter that resists changes in motion

Mechanical Equilibrium: achieved when sum of all forces acting upon an object is zero.

• Law of Acceleration- The acceleration of an object is directly

proportional to the net force acting upon it and inversely proportional to its mass

A = force / mass

Force: push or pull done on an object that changes its state of motion

• Law of Interaction- Every action elicits an equal and opposite

reaction

FREE BODY DIAGRAMSSHOW RELATIVE MAGNITUDE AND DIRECTION OF ALL

FORCES ACTING UPON AN OBJECT IN A GIVEN SITUATION.

SPECIAL TOPICS

• Projectile motion: motion in two dimensions

Horizontal (x-axis) component of motionX = Vicosθt

Vertical (y-axis) component of motionY = Visinθt + 1/2gt2

• Uniform Circular Motion: motion in a circular path

- velocity changes in direction yet the magnitude remains constant, thus

motion is accelerate- direction of acceleration is inward due to

centripetal force

• Torque: tendency of a force to rotate an object about some axis

Torque = FI*where F = force applied perpendicularly; I =

distance of applied force from fulcrum/axis

Linear Momentum and CollisionsP = mass x velocity = mv

*where P = momentum

ENERGY• Law of conservation of energy- Energy can neither be created nor

destroyed.

MECHANICAL ENERGY: energy possessed by a body due to its position (Potential energy) or motion (Kinetic energy)

ME = PE + KE

ENERGY• Potential Energy (PE) – energy possessed by a

body due to its position, shape, and configuration

PE = mgh

• Kinetic Energy (KE) – energy of motion

KE = 1/2mv2

Work and PowerWork = Force x Distance

Power = Work / Time*unit for power is the Joule/second or simply

watt.

WAVES• A disturbance that travels through a

medium, transporting energy to another location without transporting matter

a. Transverse: particles move perpendicular to the direction of the wave

b. Longitudinal: particles move parallel to direction of the wave

c. Surface: particles undergo a circular motion

WAVE PROPERTIES

ELECTRICITY

Ohm’s LawV = IR

I – Current; unit: ampere (A)V – Voltage; unit: volt (V)

R – Resistance; unit: ohm (Ω)

ELECTRIC CIRCUITS• Series: current is constant; voltage adds up

• Parallel: current adds up; voltage is constant

OPTICS

• Reflection: change in direction of a light ray in an interface with dissimilar media so that the wave returns into the medium from which it originated

Law of ReflectionAngle of incidence = Angle of reflection

• Refraction: change in direction of a wave due to a change in its speed when passing through a different medium

Law of Refractionn1sinθ1 = n2sinθ2

PLANE MIRROSImage characteristics: virtual, upright,

same distance from the mirror as the object’s distance, same size as the object