1.3 scalar & vector quantities

1.3
Understanding Scalar &
Vector Quantities

www.myfunphysicsworld.blogspot.com

Chapter 1
Introduction To Physics

1.3
Understanding Scalar & Vector
Quantities


Learning Outcomes
Define scalar and vector
quantities
Give examples of scalar and
vector quantities


Physical Quantities
Scalar vector

Magnitude Magnitude
no direction direction

Length, mass, time Displacement,
electric current, velocity, force,
temperature, area, Acceleration,
distance, speed, Momentum, weight,
energy,density,power impulse, pressure

Conduct simple activity (pg 10)
O C
16 m
8m

A B
14 m
Physics Lab Plan
Idea : distance & displacement ;
speed & velocity

Distance = total length of the
path travelled
Displacement = distance
travelled from its initial position
to its final position


Total Displacement, time, speed/ velocity/
distanc d/m t/s m s-1 m s-1
e, s/m
A 8 8 from O to A 2.40 3.33 3.33
from O
to A
B 22 16 from O to B 5.28 4.17 3.03

C 30 14 from O to 7.65 3.92 1.83
C

O 44 0 from O to O 10.32 4.26 0.00

Displacement = distance travelled from its initial position to its final
position

Total Displacement, time, speed/ velocity/
distanc d/m t/s m s-1 m s-1
e, s/m
A 8 ___ from O to 7.51 1.07 1.07
A from O
to A
B 22 ___ from O to 15.51 1.42 1.03
B

C 30 ___ from O to 22.05 1.36 0.63
C

O 44 ___ from O to 25.50 1.73 0.00
O
Displacement = distance travelled from its initial position to its final
position

Total Displacement time, speed/ velocity/
distance , d/m t/s m s-1 m s-1
, s/m
A 9.0 9 from O to 3.13 2.87 2.87
A from O
to A
B 15.5 11.1 from O 5.34 2.90 2.08
to B from O
to B
C 24.5 6.5 from O to 8.24 2.97 0.79
C from O
to C
O 31.0 0 from O to O 10.67 2.90 0.00
from O
to O

Scalar Vector
Quantities Quantities
e.g: distance, Displacement
speed , velocity
Has Has
magnitude but magnitude
no direction and direction

Addition Scalar &
Vector Quantities


Adding Scalar Quantity
Can be added, subtracted, multiplied and
divided like ordinary numbers.

e.g:
(a) 3 kg of sand is added to 1 kg cement,
resulting mixture has a mass of 4 kg
(b) 5 liters of water are poured from a pail
that has 8 liters of water in it.
The resulting volume is 3 liters

Scalar Quantities

5 kg 10 kg

Total mass = 5 + 10
= 15 kg

Adding Vector Quantity
An arrow is used to represent the magnitude
and direction of a vector quantity.

Same direction = sum
Opposite direction = minus


eg. 1

50 N 30 N

Total Force* = 50 + 30
= 80 N
(80 N due west//to the left)

*=resultant force//net force

eg. 2

50 N 10 N

Total Force = 50 - 10
= 40 N
(40 N due west//to the left)

eg. 3

50 N 50 N

Total Force = 50 - 50
= 0N
(object is not moving//at rest//stationary)

How much is the resultant
force?


Adding Vector Quantity
An arrow is used to represent the magnitude and
direction of a vector quantity.
e.g :
velocity of airplane = 100 km/h
wind velocity = 20 km/h

(a) If same direction,
Resulting velocity of airplane= 100 + 20 = 120 km/h
(a) If opposite direction,
resulting velocity of airplane = 100 -20 = 80 km/h

Special Case:
Non-parallel vectors


Case 1

Two vectors acting at a point can be replaced
by a single vector with the same effect.

Case 2

Resultant
Vector

Two vectors acting at a point can be replaced
by a single vector with the same effect.

Homework 


1. Jeremy walked 3 m due east, and then
4 m due north.
(a) What is his total distance?
3m+4m=7m
(b) What is his displacement?
5m

5m
4m

3m www.myfunphysicsworld.blogspot.com

2. Every morning Amirul walks to Badrul’s
house which is situated 80m to the east
of Amirul’s house.
They then walks towards their school
which is 60m to the south of Badrul’s
house.
What is the distance traveled by Amirul
and his displacement from his house?


1.3 scalar & vector quantities

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