PHSYICS

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# PHSYICS - PowerPoint PPT Presentation

Is a branch of science that deals with the properties, behavior and interaction between matter and energy. PHSYICS. Subdivisions of Physics. Classical Mechanics : study of motions based on Newton’s laws of mechanics

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

### PHSYICS

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
MeasurementsHow far? How large? How much?

BASIC QUANTITIES

Length: locates position of a point in space

Time: succession of events

Mass: 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

Density: mass of an object per unit volume

EXAMPLE

What 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

How many mililiters are there in 3.45 L?

Try these:

20 seconds = ? hours

10 m/s = ? km/h

10 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.

A. Four primary directions

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)

• Positive direction of motion: acceleration
• Negative direction: deceleration

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

A = ∆V/ ∆T

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 = Vi2 + 2ad

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 indicatedby 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 DIAGRAMS

SHOW 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 motion

X = Vicosθt

Vertical (y-axis) component of motion

Y = 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 = FI

*where F = force applied perpendicularly; I = distance of applied force from fulcrum/axis

Linear Momentum and Collisions

P = 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 Power

Work = 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
• Transverse: particles move perpendicular to the direction of the wave
• Longitudinal: particles move parallel to direction of the wave
• Surface: particles undergo a circular motion
ELECTRICITY

Ohm’s Law

V = 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
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 Reflection

Angle 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 Refraction

n1sinθ1 = n2sinθ2

PLANE MIRROS

Image characteristics: virtual, upright, same distance from the mirror as the object’s distance, same size as the object