Free Measurements MCQs with Answers

241. The number of significant figures in the measurement x = 10.00300 are:

• A. 7
• B. 8
• C. 5
• D. 3

Explanation: The number of significant figures in a measurement includes all the certain digits plus the first uncertain digit. In the measurement x = 10.00300, all the digits are significant because:The digits '1' and '0' before the decimal point are significant.The digits '00300' after the decimal point are significant because they follow a non-zero digit.Thus, there are a total of 7 significant figures. Options B, C, and D are incorrect because they either overestimate or underestimate the count of significant figures.

242. During the experiment, one measured the mass of mosquito and found it 1.20 x 10^-5 kg. The number of significant figures in this case is:

• A. 3 s.f
• B. 2 s.f
• C. 5 s.f
• D. 8 s.f

Explanation: When determining the number of significant figures in a measurement, focus on the digits that are known with certainty and the first estimated digit. In this case, the mass of the mosquito was measured as 1.20 × 10^-5, with the digits 1, 2, and the exponent -5 being certain and therefore significant. The leading zero is not significant. Therefore, the correct answer is 3 significant figures.

243. During a experiment, one measured the mass of a mosquito and found it to be 1.20 x 10^-5 Kg. The numbers of significant figures in this case are:

• A. Five
• B. One
• C. Two
• D. Three

Explanation: All non zero digits are significant figures and in this case there are 3 significant or non zero digits hence option D is the right choice.

244. Which experimental teachnique reduces the systematic error of the quantity being investigated?

• A. Adjusting an ammeter to remove its zero error before measuring a current
• B. Measuring several internodal distances on a standing wave to find the mean internodal distance
• C. Measuring the diameter of a wire repeatedly and calculating the average
• D. Timing a large number of oscillations to find a period

Explanation: Systematic error means that measurements of the same thing will vary in predictable ways. Systematic errors in experimental observations usually come from the instruments which are used in measuring. So, zero error is recognized as the systematic error. Thus adjusting an instrument to remove its zero error before measuring something is the best experimental technique to reduce the systematic error of the quantity being investigated.

245. The percentage error in the measurement of mass and speed are 5% or 6% respectively the maximum error in the measurement of K.E is

• A. 17%
• B. 30%
• C. 15%
• D. 90%

Explanation: Kinetic Energy = mv^2/2Percentage Error in KE = Percentage Error in Mass + 2(Percentage Error in Speed) The question states percentage error in mass is 5% and the percentage error in speed is 6%.Putting values in the formula for Percentage Error in KE gives5 + 2(6) = 5 + 12 = 17% which is option A.

246. In a cricket match 500 spectators are counted one by one. How many significant figures will be there in the final result?

• A. 0
• B. 1
• C. 2
• D. 3

Explanation: The number 500 is a whole number and has three significant figures: the digit '5' and the two trailing zeros. Trailing zeros in a whole number without a decimal point are considered significant because they indicate the precision of the count. This is why option D is correct. Option A is incorrect because significant figures cannot be zero for a non-zero number. Option B is incorrect because '500' does not consist of only one significant digit. Option C is also incorrect because the zeros in '500' are significant, not just placeholders.

247. In a simple electrical circuit the current in a resistor is measured as (2.50 +_ 0.05) mA. The resistor is marked as having a value of 4.7 _+2%. If these value where used to calculate the power dissipated in the percentage uncertainty in the value obtained ?

• A. 2%
• B. 4%
• C. 6%
• D. 8%

Explanation: First we find out the % uncertainty in current (0.05)/2.5 x 100 = 2%. Then we note the formula of power dissipated is 12 x R so the = percentage uncertainty has to be added i.e (2+2)+2=6%As it is numerical, it can have only one possible answer.

248. If the area of a circle is equal to its circumstances tha radius os this circle is:

• A. 1
• B. 2
• C. 3
• D. 4

Explanation: Given,Area= circumference πr² = 2πrCutting π and r on both sidesr = 2

249. The force of one newton per meter square is equal to:

• A. bar
• B. atm
• C. Pascal
• D. erg

Explanation: Fact. According to the formula Pressure=Force/Area 1 N/m2 = 1 Pascal

250. The present SI unit of time is defined as:

• A. 1/24 x 1/60 x 1/60 of a mean solar day
• B. The second as defined by the electronic digital watch
• C. Duration of 9,192,631,770 vibrations of a cesium-133 atom
• D. Minute

Explanation: The SI unit of time is the second, symbolized as 's'. The modern definition is based on the cesium-133 atom's vibrations: specifically, 9,192,631,770 vibrations. This provides a highly precise standard. Option A refers to an outdated definition based on the Earth's rotation, which is variable. Option B is incorrect because digital watches use the standard definition rather than define it. Option D is incorrect because a minute is a derivative unit, not the base SI unit.