Transcript Lecture # 5

MECHANICS
VELOCITY
 V= d/t
 d-DISTANCE
 t-TIME





EXPRESSED IN (UNIT):
m/s
km/s
miles/h
km/h
VELOCITY OF LIGHT
 3 x 10 E 8 m/s
 3 x 10 E 5 km/s
 3 x 10 E 10 cm/s
 3x 10 E 11 mm/s
 186,400 miles/s
AVERAGE VELOCITY
V=Vo + Vf/2
ACCELERATION
a=Vf-Vo/t
Expressed in ( m/s E 2)
Gravity
The attraction between
two masses, such as
the earth and an object
on its surface.
Commonly referred to
as the acceleration of
gravity.
GRAVITY
 DOWNWARD ACCELERATION
 9.81m/s E 2 on the Earth
 1.6m/s E 2 on the Moon
Sir Isaac Newton
NEWTON’S LAW OF
MOTION
 I LAW---INERTIA
 II LAW---FORCE
 III LAW---ACTION/REACTION
I LAW
A BODY WILL REMAIN AT REST
OR CONTINUE TO MOVE WITH A
CONSTANT VELOCITYIN A
STRAIGHT LINE UNLESS ACTED
ON BY AN EXTERNAL FORCE
I LAW IN PRACTICE
II LAW
THE FORCE ( F) ACTED ON AN
OBJECT WITH ACCELERATION
(a) IS EQUAL TO THE MASS (m)
MULTIPLIED BY THE
ACCELERATION
F=m * a
II LAW IN PRACTICE
III LAW
FOR EVERY ACTION THERE IS
AN EQUAL AND OPPOSITE
REACTION
DIFFERENCE BETWEEN WEIGHT
AND MASS
IS THERE ANY DIFFERENCE??
WEIGHT IS THE FORCE ON A
BODY CAUSED BY THE
DOWNWARD PULL OF THE
GRAVITY
WHO IS GOING TO FALL FASTER?
IN VACCUM ELEPHANT OR
FEATHER ??
WITH THE AIR
RESISTANCE!!!
WEIGHT IS EXPRESSED IN
 NEWTONS NOT GRAMS OR KILOGRAMS
 Wt = m * g
 m –mass (kg)
 g – gravity ( m/s E 2)
GRAVITY
WITH GRAVITY OR
WITHOUT?
MOMENTUM
P=m * v
TOTAL MOMENTUM BEFEORE
INTERACTION IS EQUAL TOTAL
MOMENTUM AFTER INTERACTION
WORK




WORK = F * d
F- FORCE (N)
D- DISTANCE (m)
EXPRESSED IN
JOULES (J)
POWER
 P=WORK/TIME
 EXPRESSED IN WATTS (W)
ENERGY IS THE ABILITY TO
DO WORK
POTENTIAL ENERGY




PE = m * g * h
m- mass (g)
g- gravity ( m/s E 2)
h- height (m)
KINETIC ENERGY
 KE = ½ m * v E 2
 m – mass (m)
 Velocity (m/s)
POTENTIAL & KINETIC
TRANSFER OF ENERGY
TRANSFER OF ENERGY
 ELECTRIC-THERMAL-KINETIC-ELECTROMAGNETIC
HEAT
 IS THE KINETIC
ENERGY OF THE
RANDOM MOTION
OF MOLECULES
HEAT TRANSFER
CONDUCTION
CONVECTION
RADIATION
CONDUCTION
TRANSFER OF HEAT BY TOUCH
CONVECTION
MECHANICAL TRANSFER
OF HOT MOLECULES IN A
LIQUID OR GAS
RADIATION
TRANSFER OF ENERGY
THROUGH SPACE
Temperature Scales
TEMEPERATURE
CONVERSION
 Tc = 5/9 ( F-32)
 Tf = (9/5 C) + 32
 Tk = Tc + 273