physics : class11 Dimensions and Units of Surface Tension : Surface Tension : Properties of Bulk Matter MCQ Questions and Answers
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Dimensions and Units of Surface Tension
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 of the following is dimensionally equivalent to the SI unit of surface tension?
A.
kg m s^-2
B.
kg s^-2
C.
kg m^-1 s^-2
D.
kg m^2 s^-2
Correct Answer:
kg s^-2
Explanation:
The SI unit of surface tension is N m^-1. Since 1 N = 1 kg m s^-2, N m^-1 = kg s^-2.
3. A liquid has surface tension 0.072 N m^-1. What is its value in dyn cm^-1?
A.
0.0072 dyn cm^-1
B.
0.72 dyn cm^-1
C.
72 dyn cm^-1
D.
720 dyn cm^-1
Correct Answer:
72 dyn cm^-1
Explanation:
Using 1 N = 10^5 dyn and 1 m = 100 cm, 1 N m^-1 = 10^3 dyn cm^-1. Therefore, 0.072 N m^-1 = 72 dyn cm^-1.
4. Which expression represents the dimensions of surface tension in terms of energy and area?
A.
Energy multiplied by area
B.
Energy divided by area
C.
Area divided by energy
D.
Energy divided by length
Correct Answer:
Energy divided by area
Explanation:
Surface tension can be expressed as surface energy per unit area. Energy has dimensions [M L^2 T^-2], and division by area [L^2] gives [M T^-2].
5. Which of the following units is exactly equivalent to 1 N m^-1?
A.
1 J m^-2
B.
1 J m^-1
C.
1 W m^-2
D.
1 Pa m^-2
Correct Answer:
1 J m^-2
Explanation:
Since 1 J = 1 N m, dividing by m^2 gives 1 J m^-2 = 1 N m^-1, the unit of surface tension.
6. A surface tension value is given as 25 dyn cm^-1. What is its SI value?
A.
0.0025 N m^-1
B.
0.025 N m^-1
C.
2.5 N m^-1
D.
25 N m^-1
Correct Answer:
0.025 N m^-1
Explanation:
Since 1 dyn cm^-1 = 10^-3 N m^-1, 25 dyn cm^-1 = 25 × 10^-3 N m^-1 = 0.025 N m^-1.
7. Which combination of fundamental SI units has the dimensions of surface tension?
A.
kg m s^-2
B.
kg s^-2
C.
kg m^-1 s^-2
D.
kg m^2 s^-2
Correct Answer:
kg s^-2
Explanation:
Surface tension equals force per length. Substituting force as kg m s^-2 and dividing by m results in kg s^-2.
8. The dimensions of surface tension can also be written as the dimensions of:
A.
Pressure multiplied by length
B.
Pressure divided by length
C.
Force multiplied by length
D.
Power divided by area
Correct Answer:
Pressure multiplied by length
Explanation:
Pressure has dimensions [M L^-1 T^-2]. Multiplying by length gives [M T^-2], which is the dimensional formula of surface tension.
9. In a system where the unit of mass is twice the SI kilogram while the unit of time remains unchanged, the numerical value of a surface tension expressed in the new units will be:
A.
Twice its SI numerical value
B.
Half its SI numerical value
C.
Four times its SI numerical value
D.
Unchanged from its SI numerical value
Correct Answer:
Half its SI numerical value
Explanation:
Surface tension has dimensions M T^-2. If the mass unit becomes twice as large and the time unit is unchanged, one new unit of surface tension is twice the SI unit. Hence its numerical value becomes half.
10. A proposed unit for surface tension is kg m^2 s^-2 m^-2. Which conclusion is correct?
A.
It has the dimensions of pressure
B.
It has the dimensions of force
C.
It has the dimensions of surface tension
D.
It has the dimensions of power
Correct Answer:
It has the dimensions of surface tension
Explanation:
The proposed unit simplifies to kg s^-2 because m^2 cancels with m^-2. Since surface tension has SI dimensions kg s^-2, the proposed unit is valid.
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