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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

PHSYICS

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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

### Conversion of Units

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.

### 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

• Positive direction of motion: acceleration

• 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 = Vi2 + 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 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: 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 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

• 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 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