Tuesday, 27 March 2012

Scalar Quantities and Vector Quantities

Scalar Quantity:

1.      A scalar quantity has magnitude only (e.g. distance travelled – 1 km).

2.      Final scalar quantities can be found by simple additions and subtractions of like scalar quantities involved.

(Note: Pressure is a scalar quantity)

Vector Quantity 

1.      A vector quantity has both magnitude and direction (e.g. displacement – 1 km due East).

2.      Resultant vector quantities can be found by graphical methods to account for the magnitudes and directions of each individual like vector quantities involved.

3.      Vector variables (e.g. displacement, s) are written in bold.

4.      Examples of Scalar & Vector Quantities:

Scalar Quantities                   Vector Quantities
Length                                      Displacement
Mass                                        Weight (mg)
Time                                         Acceleration; Gravitational Acceleration, g;
            Temperature                             Momentum; Impulse
            Current                                     Force; Impulsive Force; Gravitational Force
            Speed                                      Velocity
            Pressure (acts in all directions in fluids)

Which one is a vector quantity?
2007 P1 Q2 pg. 92: A Energy; B Power; C Force; D Pressure? (Answer:: C)
2009 P1 Q2 pg 186: A Area; B Length; C Distance; D Displacement? (Answer: D)
2012 P1 Q3 pg. 332: A Energy; B Force; C Mass; D Speed? (Answer: B)


Segment Review Questions:

A)  Scalar Quantity and Vector Quantity

1.        State the main difference between a scalar quantity and a vector quantity.

2.        An object moves 40 km on a bearing of 090 from O to A in 20 minutes; it then immediately moves north 30 km also in 20 minutes to B. Find:

a.       The total distance travelled by the object from O to B
b.      The final displacement of the object in moving from O to B in terms of both magnitude and bearing from O.
c.       For the whole journey from O to B:
                                                               i.      The object’s average speed
                                                             ii.      The object’s average velocity

3.        Is pressure a scalar or vector quantity? Name 5 scalar quantities.

4.        Name 5 vector quantities and state their respective SI units of measurement.

Updated on 24/01/2013 by

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