417277628-Physics-General Physics 1(Mechanics and Heat)for Sciences and Engineering Faculties

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1. Nour Elsawy

PHYSICS

12.01.2017

2. SI UNITS
SI base units
The SI is founded on seven SI base units for seven base
quantities assumed to be mutually independent, as given in Table 1.
They can not be defined in terms of other physical quantities.

Table 1. SI base units


SI base unit

Base quantity Name Symbol
Length meter m
Mass kilogram kg
Time second s
electric current ampere A
thermodynamic
temperature
kelvin K
amount of matter mole mol
luminous intensity candela cd





SI derived units
Other quantities, called derived quantities, are defined in terms of the
seven base quantities via a system of quantity equations. The SI
derived units for these derived quantities are obtained from these
equations and the seven SI base units. Examples of such SI derived
units are given in Table 2, where it should be noted that the symbol 1
for quantities of dimension 1 such as mass fraction is generally
omitted.

3. Table 2. Examples of SI derived units


SI derived unit

Derived quantity formula Symbol
Area square meter m
2

Volume cubic meter m
3

speed, velocity Distance/time m/s
Acceleration Velocity/time m/s
2

Force Mass x acceleration
Kg x
m/s
2
Energy
Mass x acceleration x
height
Kg x
m
2
/s
2
Energy 1/2mass x velocity
2

Kg x
m
2
/s
2

Power Energy/time
Kg x
m
2
/s
3

pressure Force/area
Kg/s
2
x
m
Density Mass/volume kg/m
3

4. Projectiles Motion

 Projectile motion is two-dimensional
 A projectile is an object upon which the only force acting is
gravity.



There are a variety of examples of projectiles:
 An object dropped from rest is a projectile (provided that the
influence of air resistance is negligible).
 An object that is thrown vertically upward is also a projectile
(provided that the influence of air resistance is negligible).
 And an object which is thrown upward at an angle to the
horizontal is also a projectile (provided that the influence of air
resistance is negligible).

5. Uncerainty


Completing Uncertainty Calculations:
1) Addition and Subtraction: ADD the Absolute Uncertainties
Rule:
(AA)+(BB)=(A+B)
(A A) - (B B) = (A-B)
2) Multiplication and Division:
Rule:
(AA)x(BB)=(AxB)x(AxB))
(AA)/(BB)=(A/B)x(A/B))
3) For a number raised to a power
Rule:EX:
(AA)
2
x(BB)
3
=(A
2
xB
3
)((2xA/A+3xB/B)x(A
2
xB
3
)




6. Scalar and Vector


 Scalars are quantities that are fully described by a
magnitude (or numerical value) alone.
 Vectors are quantities that are fully described by both a
magnitude and a direction.

7. Homogeneity

In physics, a homogeneous material or system has the same
properties at every point; it is uniform without irregularities.

For example:

Speed=Velocity
LHS RHS
Speed=d/t velocity=d/t
=L/T =L/T
L/T=L/T




















The units of
both sides
must be equal

8. Newton’s Laws
-first law:
-law of inertia:
-anybody at rest tends to start at rest and anybody motion tends to
stay in motion
-unit an external factor acts on it
f=0
-inertia= tendency of the body to keep its last state

-second law:
-the force is equal to the product of mass and acceleration
-the acceleration is inversely proportional to the mass and directly to
the force
-the force is equal to the rate of charge in momentum
-f = m x a
f.force in N
mmass in kg
a acceleration in m/s
2

-W = m x g
Wweight in N
mmass in kg
ggravity = 10m/s
2

-f = P / t

9. fforce in N
Pchange in momentum in kg x m / r
ttime in s

-third law:
-for every action there is a reaction equal in magnitude and opposite
in direction

10. Motion


Motion is a change of position of an object


Equations of Motion: