Measurements and Uncertainties Practice Questions
IB (International Baccalaureate) · IB Physics HL · 150 free MCQs with instant results and detailed explanations.
150
Total
53
Easy
76
Medium
21
Hard
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Sample Questions from Measurements and Uncertainties
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Q1
Easy
What is the primary purpose of using significant figures in measurements?
A.
To indicate the precision of a measurement.
B.
To simplify calculations.
C.
To convert units easily.
D.
To ensure measurements are always whole numbers.
Show Answer & Explanation
Correct Answer: A
Significant figures indicate the precision of a measurement by showing which digits are meaningful based on the measurement's uncertainty.
Q2
Easy
If a measurement is recorded as 75.0 m, how many significant figures does it contain?
A.
2
B.
3
C.
4
D.
1
Show Answer & Explanation
Correct Answer: B
The measurement 75.0 m has three significant figures; the digits '7', '5', and the trailing zero after the decimal point are all significant.
Q3
Easy
A ruler measures a length as 25.3 cm with an uncertainty of ยฑ0.1 cm. What is the range of the actual length?
A.
25.2 cm to 25.4 cm
B.
25.1 cm to 25.5 cm
C.
25.3 cm to 25.4 cm
D.
25.0 cm to 25.6 cm
Show Answer & Explanation
Correct Answer: A
The range is calculated by subtracting and adding the uncertainty (ยฑ0.1 cm) to the measured value (25.3 cm), resulting in 25.2 cm to 25.4 cm.
Q4
Medium
What is the primary source of uncertainty in a measurement taken with a digital multimeter?
A.
Calibration error
B.
Zero error
C.
Resolution error
D.
Systematic error
Show Answer & Explanation
Correct Answer: C
Resolution error is the smallest change in a measured quantity that can be detected by a measuring instrument. For a digital multimeter, this often determines the precision of the displayed value, making it a significant source of uncertainty.
Q5
Medium
A student measures the length of a metal rod as 25.0 cm ยฑ 0.2 cm. What is the relative uncertainty in this measurement?
A.
0.008
B.
0.02
C.
0.0080
D.
0.002
Show Answer & Explanation
Correct Answer: C
Relative uncertainty is calculated as the absolute uncertainty divided by the measured value. Here, it's 0.2 cm / 25.0 cm = 0.0080.
Q6
Medium
If a pendulum has a measured period of 2.00 s with an uncertainty of ยฑ0.05 s, what is the percentage uncertainty in the period?
A.
2.5%
B.
0.25%
C.
5.0%
D.
0.5%
Show Answer & Explanation
Correct Answer: A
Percentage uncertainty is found by (absolute uncertainty / measured value) x 100. Here, it is (0.05 s / 2.00 s) x 100 = 2.5%.
Q7
Medium
In an experiment, a student finds that the time taken for a reaction is 12.0 s with an uncertainty of ยฑ0.5 s. If the reaction occurs 3 times, how should the student report the average time taken?
A.
12.0 s ยฑ 0.5 s
B.
12.0 s ยฑ 0.3 s
C.
12.0 s ยฑ 0.2 s
D.
12.0 s ยฑ 0.1 s
Show Answer & Explanation
Correct Answer: B
When averaging repeated measurements, the uncertainty is divided by the square root of the number of measurements. This gives ยฑ(0.5 s / โ3) = ยฑ0.3 s.
Q8
Hard
A measuring instrument has a least count of 0.1 mm. If a length is measured as 25.6 cm, what is the absolute uncertainty in this measurement?
A.
0.01 cm
B.
0.1 cm
C.
0.05 cm
D.
0.001 cm
Show Answer & Explanation
Correct Answer: B
The absolute uncertainty is typically equal to half of the least count of the measuring instrument. Here, the least count is 0.1 mm, which is equivalent to 0.01 cm, so the absolute uncertainty is 0.1 cm.
Q9
Hard
A measuring instrument has a systematic error of +0.5 cm and a random uncertainty of ยฑ0.2 cm. If you measure an object that is 10.0 cm long, what is the best estimate of its length and the associated uncertainty?
A.
10.0 ยฑ 0.7 cm
B.
10.5 ยฑ 0.2 cm
C.
10.0 ยฑ 0.5 cm
D.
10.5 ยฑ 0.7 cm
Show Answer & Explanation
Correct Answer: D
The best estimate includes the systematic error (10.0 cm + 0.5 cm = 10.5 cm) and combines the random uncertainty (ยฑ0.2 cm). The total uncertainty is calculated as the combination of systematic and random uncertainties, resulting in 10.5 ยฑ 0.7 cm.
Q10
Hard
A student measures the resistance of a wire and records a value of 15.0 ฮฉ with an uncertainty of ยฑ0.5 ฮฉ. If the student also measures the voltage across the wire as 30.0 V with an uncertainty of ยฑ1.0 V, what is the percentage uncertainty in the calculated power (P = Vยฒ/R)?
A.
8.33%
B.
10.00%
C.
11.11%
D.
12.50%
Show Answer & Explanation
Correct Answer: C
To find the percentage uncertainty in power, we first need the power formula P = Vยฒ/R. Using the rules of uncertainty propagation, we find that the percentage uncertainty in power is approximately 11.11%, which comes from combining the uncertainties in voltage and resistance appropriately.
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Measurements and Uncertainties โ IB (International Baccalaureate) IB Physics HL Practice Questions Online
This page contains 150 practice MCQs for the chapter Measurements and Uncertainties in IB (International Baccalaureate) IB Physics HL. The questions are organized by difficulty โ 53 easy, 76 medium, 21 hard โ so you can choose the right level for your preparation.
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