Page 11 - Q & A STPM 2022 Physics

Physics Semester 1 STPM Chapter 1 Physical Quantities and Units
Question 3

–1
–2
2
2
The permittivity of free space e has units A s N m and the permeability of
0
free space µ has units N A . Their relationship is as shown in the equation below.
–2
0 1
k =
2
e µ 0
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0
Determine the appropriate unit for k.
–1
2
A m s A C m s –2
2
–1
B m s A 2 D m s –1
Answer: D 1 1 1 1
Semester
2
1 Unit for = e µ 0 = A s N m –2 NA –2 = s m –2 = m s –2
2 2
–1
2
0
Unit for k = m s –1
1.2 Dimensions of Physical Quantities
Section A Multiple-choice Questions
Question 1
The drag force F is related to the density ρ and velocity v by the equation
2
F = kρv .
Where k is a constant. The dimension of the constant k is
A M L 2 C L 2
B L T 2 D L –2

Answer: C
–3
–2
[F] = M L T [ρ] = M L [v] = L T –1
k = F
ρv 2
M L T –2
[k] = = L 2
2
ML L T –2
–3

Exam Tips
Exam Tips
Base quantities and their dimensions:
Mass (M), length (L), time (T), current (A), temperature (θ), quantity of matter (N).

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01 STPM Q&A PHY T1.indd 2 17/02/2022 10:03 AM