Transcript Physics Lecture Resources Prof. Mineesh Gulati Head-Physics Wing Happy Model Hr. Sec. School, Udhampur, J&K Website: happyphysics.com happyphysics.com Chapter 1 Units, Physical Quantities, and vectors 1.1 The Nature of.

Physics Lecture Resources
Prof. Mineesh Gulati
Head-Physics Wing
Happy Model Hr. Sec. School, Udhampur, J&K
Website: happyphysics.com
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Chapter 1 Units,
Physical Quantities, and
vectors
1.1 The Nature of Physics

Physical theory Creativity at
every stage
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1.3 Standard and Units


Any number that is used to describe a physical
phenomenon quantitatively is called physical
quantity
The most common unit used by scientists and
engineers around the world is International
System, SI
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SI unit






Time: second [s]
Length: meter [m]
Mass: kilogram [kg]
Current: ampere [A]
Temperature: kelvin [K]
Force: newton [N]
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Unit Prefixes





1 nm = 10-9m
1μm= 10-6m
1 mm= 10-3m
1 cm = 10-2m
1 km = 103m
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1.4 Unit Consistency and Conversions

Equation must always be dimensionally
consistent
example: d= 10m, v = 2ms-1 and t = 5s
 m
10m   2   5s 
 s
© 2005 Pearson Education
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1.5 Uncertainty and Significant Figures


Uncertainty is the maximum different between
the measured vale and true value
Significant figures is used to indicated the
number of meaningful digits
example:
2.91mm ( 3 significant figures )
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Table 1.1
Mathematical operation Significant figures in result
Multiplication or division
No more than in number with
the fewest significant figures
e.g. 0.745 x 2.2/3.885=0.42
Addition or subtraction
Determined by the number
with the smallest uncertainty
e.g.27.153+138.2–11.74=153.6
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1.7 Vectors and Vector Addition

Scalar quantity is described by a single real
number, it can be positive, zero or negative

Vector quantity has both a magnitude and a
direction in space.
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Displacement

Displacement is the change of position of a
point
P2 The displacement form
P1
A
point P1 to P2 is vector
A
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Displacement
P2


P1
Displacement is always a
straight-line segment
directed from the starting
point to the end point
If the path ends at the
same place where it
started, the displacement
is zero
Displacement is not related directly
to the distance traveled
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Vector Addition
B
A
C =A+B
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A
B
C = A+ B
A
B
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C
A
R
B
D
R = ( A+B ) + C
=D+C
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Addition of vectors
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1.8 Components of Vectors
A  Ax  Ay
Ay
A
θ
Ax
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Ax
 cos 
A
Ay
 sin 
A
Ay
tan  
Ax
Rx  Ax  Bx
By
R
Ry
Ay
B
Ry  Ax  By
Bx
A A A
A
Ax
2
x
Rx
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2
y
1.9 Unit Vectors
A unit vector is a vector that has a magnitude of 1
A  Ax i  Ay j
Vector sum R:
R  A B
 ( Ax i  Ay j )  ( Bx i  By j )
 ( Ax  Bx )i  ( Ay  By ) j
 Rx i  Ry j
A
Ayj
j
i
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Axi
1.10 Products of Vectors

Dot product
B
θ
A
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Example 1.10
Find the scalar product of the two vectors. The
magnitude of vectors are A=4.0 and B=5.0
Ans:
B
130°
= 4 ×5 cos 77°
A
53°
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=4.5

Vector Product
i
A×B
j
k
A  B  Ax
Ay
Az
Bx
By
Bz
B
θ
A
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Right hand rule
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Summary
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END
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