Online Test — Units and Measurements
20 Questions • 15 min • Chapter MCQ
15:00
Question 1 of 20
How many fundamental (base) units are there in the SI system?
5
6
7
9
Explanation: SI has seven base units: metre, kilogram, second, ampere, kelvin, mole and candela.
Question 2 of 20
Which of the following is a derived unit?
kelvin
mole
newton
candela
Explanation: The newton (kg m s^-2) is derived; the other three are SI base units.
Question 3 of 20
A speed of 90 km/h in m/s is:
20
25
30
32
Explanation: Multiply by 5/18: 90 × 5/18 = 25 m/s.
Question 4 of 20
The SI prefix 'nano' represents a factor of:
10^-3
10^-6
10^-9
10^-12
Explanation: Nano = 10^-9; milli = 10^-3, micro = 10^-6, pico = 10^-12.
Question 5 of 20
The dimensional formula of force is:
[M L T^-1]
[M L T^-2]
[M L^2 T^-2]
[M L^2 T^-3]
Explanation: Force = mass × acceleration = [M][L T^-2] = [M^1 L^1 T^-2].
Question 6 of 20
Which physical quantity is dimensionless?
pressure
strain
momentum
power
Explanation: Strain is a length-to-length ratio, so [M^0 L^0 T^0].
Question 7 of 20
The dimensional formula [M L^2 T^-2] represents:
power
force
energy
pressure
Explanation: Work/energy has dimensions [M^1 L^2 T^-2]; power adds a T^-1.
Question 8 of 20
Which pair has the SAME dimensions?
work and power
work and torque
force and momentum
pressure and force
Explanation: Both work and torque have dimensions [M^1 L^2 T^-2].
Question 9 of 20
The principle of homogeneity requires that, in a valid equation:
all terms have equal numerical value
all added or equated terms have the same dimensions
all constants are integers
both sides are positive
Explanation: Only quantities with identical dimensions may be added, subtracted or equated.
Question 10 of 20
Dimensional analysis CANNOT:
check an equation
convert units between systems
find a dimensionless constant
give the dimensions of a derived quantity
Explanation: A pure number such as 1/2 in (1/2)mv^2 cannot be obtained from dimensions.
Question 11 of 20
The number of significant figures in 0.00308 is:
2
3
4
5
Explanation: Leading zeros don't count; the digits 3, 0 and 8 do — three significant figures.
Question 12 of 20
The number of significant figures in 4.700 is:
2
3
4
5
Explanation: Trailing zeros after a decimal point are significant, giving four.
Question 13 of 20
When two quantities are multiplied, their errors combine by adding the:
absolute errors
relative errors
squares of errors
least counts
Explanation: For products and quotients, the relative (fractional) errors add.
Question 14 of 20
If Z = A^3, the relative error in Z is:
ΔA/A
2 ΔA/A
3 ΔA/A
(ΔA/A)^3
Explanation: For a power, the relative error is multiplied by the exponent: 3 ΔA/A.
Question 15 of 20
Closeness of repeated measurements to one another describes:
accuracy
precision
error
true value
Explanation: Precision is the agreement among repeated readings; accuracy is closeness to the true value.
Question 16 of 20
A zero error in a vernier callipers is an example of:
random error
systematic error
gross error
no error
Explanation: A consistent offset present in every reading is a systematic error.
Question 17 of 20
The result of 2.5 × 1.25, rounded to correct significant figures, is:
3.125
3.1
3.13
3
Explanation: The least-precise factor (2.5) has two significant figures, so the product is 3.1.
Question 18 of 20
The dimensional formula of the gravitational constant G is:
[M^-1 L^3 T^-2]
[M L^3 T^-2]
[M^-1 L^2 T^-2]
[M L^2 T^-1]
Explanation: From F = G m1 m2 / r^2, G = F r^2 / (m1 m2) = [M^-1 L^3 T^-2].
Question 19 of 20
1 newton equals how many dynes?
10^3
10^5
10^6
10^7
Explanation: 1 N = 1 kg m s^-2 = (10^3 g)(10^2 cm) s^-2 = 10^5 dyne.
Question 20 of 20
Adding 12.3 m, 0.45 m and 6.789 m to correct significant figures gives:
19.539 m
19.5 m
19.54 m
20 m
Explanation: Sum = 19.539 m; the term with fewest decimals (12.3) has one, so report 19.5 m.