Page 37 - Physics - XI

Q25. There are two physical balances: one with equal arms and other with unequal arms. Which
one should be preferred? What additional steps do you need to take to use a physical balance
with unequal arms? (NCERT)
Ans. Physical balance with equal arms will be preferred. If a balance with unequal arms is used, the mass
to be measured by putting it in pan P will again be measured by putting it in pan P and then an
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average of those readings will be taken. 2

Q26. The minimum mass that can be used from the weight box is 10 g. Find the possible instrumental
error. (NCERT)
Ans. The minimum mass that can be used from the weight box is 10 g which means the least accurate
measurement of the mass is also 10 g. So, the possible instrumental error should also be 10 grams.
Q27. Instead of placing the mass (say a steel block) on the pan, suppose it is hanged from the same

hook S on which the pan P is hanging. Will the value of measured mass be same or diff erent?
1
1
(NCERT)
Ans. Since the physical balance works on the principle of moment, therefore, the value of measured mass
will be the same. This is because regardless of its position in a pan, the gravitational force exerted
by that mass remains the same.

COMPETENCY-BASED QUESTIONS
COMPETENCY-BASED QUESTIONS

Multiple Choice Questions
Q1. The least count of a Vernier Calliper is also known as

a. Vernier count b. Vernier sample c. Vernier constant d. Vernier calibration
Q2. The least count of a Vernier Calliper is ________.

a. 1 mm b. 0.1 mm c. 0.001 mm d. 10 mm
Q3. The diff erence between the value of one main scale division and one Vernier scale division is
known as

a. least count b. resolution c. actual reading d. none of these
Q4. Zero error is given by the formula

a. Actual reading = Main scale – Vernier scale – (Zero error)
b. Actual reading = Main scale + Vernier scale – (Zero error)

c. Actual reading = Main scale + Vernier scale + (Zero error)
d. Actual reading = Main scale × Vernier scale – (Zero error)

Q5. n-divisions on the main scale of a Vernier Calliper coincide with n + 1 divisions on the Vernier
scale. If each division on the main scale is of x units, then the least count of the instrument is
n 1 n x
x
a. b. c. d.
n +1 n +1 n +1 n +1
Q6. A student measured the diameter of a wire using a screw gauge with the least count of 0.001
cm and listed the measurements. The correct measurement is
a. 5.3 cm b. 5.32 cm c. 5.320 cm d. 5.3200 cm

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