chemistry : class11 Surface Tension Units and Dimensions : Surface tension : States of Matter: Gases and Liquids MCQ Questions and Answers
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Surface Tension Units and Dimensions
MCQ questions and answers.
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MCQ Questions
1. What is the dimensional formula of surface tension?
A.
[M L T^-2]
B.
[M T^-2]
C.
[M L^-1 T^-2]
D.
[M L^2 T^-2]
Correct Answer:
[M T^-2]
Explanation:
Surface tension is force per unit length. Since force has dimensions [M L T^-2], dividing by length gives [M T^-2].
2. Which SI unit is dimensionally and physically equivalent to joule per square metre for measuring surface tension?
A.
N m^-2
B.
N m
C.
N m^-1
D.
J m^-1
Correct Answer:
N m^-1
Explanation:
Surface tension equals surface energy per unit area. Therefore, J m^-2 = (N m) m^-2 = N m^-1.
3. A liquid has a surface tension of 72 dyn cm^-1 in the CGS system. What is its value in SI units?
A.
7.2 × 10^-2 N m^-1
B.
7.2 × 10^-1 N m^-1
C.
7.2 × 10^1 N m^-1
D.
7.2 × 10^-4 N m^-1
Correct Answer:
7.2 × 10^-2 N m^-1
Explanation:
Since 1 dyn cm^-1 = 10^-3 N m^-1, 72 dyn cm^-1 equals 72 × 10^-3 N m^-1 = 7.2 × 10^-2 N m^-1.
4. Which of the following has the same dimensions as surface tension?
A.
Pressure
B.
Energy per unit area
C.
Energy per unit volume
D.
Force per unit area
Correct Answer:
Energy per unit area
Explanation:
Surface tension can be expressed as surface energy per unit area. Its dimensions are therefore [M L^2 T^-2] divided by [L^2], giving [M T^-2].
5. The SI value of a surface tension is 0.045 N m^-1. What is its value in dyn cm^-1?
A.
0.45 dyn cm^-1
B.
4.5 dyn cm^-1
C.
45 dyn cm^-1
D.
450 dyn cm^-1
Correct Answer:
45 dyn cm^-1
Explanation:
Because 1 N m^-1 = 1000 dyn cm^-1, 0.045 N m^-1 = 0.045 × 1000 = 45 dyn cm^-1.
6. A proposed unit for surface tension is kg s^-2. Is this unit dimensionally valid?
A.
No, because surface tension has dimensions kg m^-1 s^-2
B.
No, because surface tension has dimensions kg m s^-2
C.
Yes, because [M T^-2] is the dimension of surface tension
D.
Yes, because surface tension has dimensions kg m^2 s^-2
Correct Answer:
Yes, because [M T^-2] is the dimension of surface tension
Explanation:
The dimensional formula of surface tension is [M T^-2]. In SI base units, this is kg s^-2, so the proposed unit is valid.
7. Which conversion factor is correct for surface tension units?
A.
1 dyn cm^-1 = 10^-2 N m^-1
B.
1 dyn cm^-1 = 10^-3 N m^-1
C.
1 dyn cm^-1 = 10^2 N m^-1
D.
1 dyn cm^-1 = 10^-5 N m^-1
Correct Answer:
1 dyn cm^-1 = 10^-3 N m^-1
Explanation:
Using 1 dyn = 10^-5 N and 1 cm = 10^-2 m, 1 dyn cm^-1 = 10^-5 N divided by 10^-2 m = 10^-3 N m^-1.
8. The dimensions of surface tension are identical to those of which quantity?
A.
Momentum
B.
Impulse
C.
Work divided by area
D.
Force multiplied by length
Correct Answer:
Work divided by area
Explanation:
Work has dimensions [M L^2 T^-2]. Dividing by area [L^2] gives [M T^-2], which is the dimensional formula of surface tension.
9. A student writes the unit of surface tension as J m^-2 and another writes it as N m^-1. Which statement is correct?
A.
Only J m^-2 is correct because surface tension is energy
B.
Only N m^-1 is correct because surface tension is force
C.
Both are correct because J m^-2 is dimensionally equivalent to N m^-1
D.
Neither is correct because surface tension is measured in N m^-2
Correct Answer:
Both are correct because J m^-2 is dimensionally equivalent to N m^-1
Explanation:
Since 1 J = 1 N m, J m^-2 equals N m m^-2 = N m^-1. Both units represent surface tension.
10. A quantity has the dimensions [M T^-2] and is expressed as 0.08 kg s^-2. When written in N m^-1, its numerical value is:
A.
0.008
B.
0.08
C.
0.8
D.
8.0
Correct Answer:
0.08
Explanation:
Since 1 N m^-1 = (kg m s^-2) m^-1 = kg s^-2, the numerical value remains 0.08 N m^-1.
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