Free Measurements MCQs with Answers

31. The velocity of a particle is related to time according to the equation V= ct3. The dimensions of constant:

• A. L-1T-1
• B. LT-3
• C. LT -4
• D. L-2T-2

Explanation: The following is the solution:For the principle of homogeneity:V =ct3(LT-1) =c(T3)c =LT-1/T3c =LT-4.

32. In the SI system of units, the fundamental units of length, mass, and time are _, _ and _ respectively:

• A. Meter, Kilogram and Kilo second
• B. Kilometre, Kilogram and Hour
• C. Meter, Kilogram, and Second
• D. Centimetre, Centigram and Second

Explanation: The following is the solution:Meter (m) remains the same as in options (a) and (b).Kilogram (kg) remains the same as in options (a) and (b).Second (s) is the base unit of time in the SI system, representing the duration of 9,192,631,770 periods of the radiation corresponding to the transition between two hyperfine levels of the ground state of the cesium-133 atom.

33. Molar mass of water is:

• A. 0.018 kg/mol
• B. 0.108 kg/mol
• C. 0.027 kg/mol
• D. 0.0635 kg/mol

Explanation: The average mass of one H2O molecule is 18.02 amu. The number of atoms is an exact number, the number of mole is an exact number; they do not affect the number of significant figures. The average mass of one mole of H2O is 18.02 grams. This is stated: the molar mass of water is 18.02 g/mol or 0.018kg/mol.

34. What is 1 radian in degrees approximately:

• A. 57.3 degrees
• B. 360 degrees
• C. π degrees
• D. π2 degrees

Explanation: The following is the solution:1 rad × 180/π = 57.296°

35. Percentage uncertainty in length and width of a rectangle is 2% and 3%. The total uncertainty in the area of that rectangle is:

• A. 1.5%
• B. 5%
• C. 1%
• D. 6%

Explanation: The following is the solution:Area = length x widthRelative uncertainties are added, when two quantities are multiplied.For addition or subtraction: The uncertainties add up directly.For multiplication or division: The relative uncertainties (expressed as a fraction or percentage) add up directly. To obtain the absolute uncertainty, multiply the combined relative uncertainty by the result of the multiplication or division.For powers or roots: Multiply the absolute uncertainty by the power or root exponent.

36. The diameter of a wire is measured by using a micrometer screw gauge with least count of 0.01 mm. Which of the following readings will be correct?

• A. 0.20 cm
• B. 0.002 m
• C. 2.00 mm
• D. 0.2 cm

Explanation: The following is the solution:Since least count is 0.01 mm, therefore, diameter must be expressed in multiples of 0.01.2.00 mm is 200 times 0.01 mm therefore, (C).

37. Force is a derived quantity, its derived unit can be expressed in terms of the base units as:

• A. Kgms-2
• B. Kgcms-2
• C. Kgm2s2
• D. Kgms2

Explanation: The following is the solution:Since F=ma ,where m: mass in kg,a: acceleration in m/s²,F = Kgms-2 = Newton

38. 1 light year distance is the:

• A. Distance travelled by earth in one year
• B. Distance travelled by a star in one year
• C. Distance travelled by light in one year
• D. Distance travelled by light in one galactic year

Explanation: A light-year is defined as the distance that light travels in one year in a vacuum. Since light travels at a constant speed of approximately 299,792 kilometers per second (in vacuum), the distance it travels in one year is about 9.461 trillion kilometres (or about 5.879 trillion miles).

39. Which of the following is not a unit of energy?

• A. Calorie
• B. None of these
• C. Kilowatt
• D. Joule

Explanation: 'Kilowatt' is a unit of power. Calorie and joule, on the other hand, are the units of energy where one calorie is equal to 4.18 J.

40. Vector is quantity which:

• A. Has direction
• B. Has magnitude
• C. Follow rules of vector addition
• D. Derived from time only

Explanation: All vectors follow rules of vector addition. They have both; magnitude and direction. There exist vector quantities which are not derived with respect to time (eg: area)