Page 117 - Physics - XI

Q5. If M is the mass of water that rises in a capillary tube of radius r, then mass of water which
will rise in a capillary tube of radius 2r is
M
a. 2M b. 4M c. d. M
2
Q6. Pressure inside two soap bubbles are 1.01 atm and 1.02 atm, respectively. The ratio of their

volume is
a. 4 : 1 b. 0.8 : 1 c. 8 : 1 d. 2 : 1
Q7. An air bubble of radius 1 cm in water has an upward acceleration 9.8 cm/s . The density of
2
water is 1 g/cm and water off ers negligible drag force on the bubble. The mass of the bubble
3
is
(Take, g = 9.8 m/s ).
2
a. 4.51 g b. 4.15 g c. 3.15 g d. 1.52 g

Answer key
1. (c), 2. (a), 3. (d), 4. (a), 5. (a), 6. (c), 7. (b)

Assertion-Reason Type Questions

These consist of two statements– Assertion (A) and Reason (R). Answer these questions by selecting
the appropriate option given below:
a. Both A and R are true and R is the correct explanation of A.
b. Both A and R are true and R is not the correct explanation of A.

c. A is true but R is false.
d. A is false but R is true.

1. Assertion(A) : Oil drops spread on cold water and remains as a drop on hot water.
Reason(R) : Surface tension of oil is less than that of cold water and more than that of hot
water.
2. Assertion(A) : Small drops of mercury are spherical and large drops are fl at.

Reason(R) : Surface tension of small drops is infi nite.
3. Assertion(A) : Water fl ows faster than honey.

Reason(R) : The coeffi cient of viscous force of water is less than honey.
4. Assertion(A) : Flags fl utter in breeze.
Reason(R) : There will be unequal pressure on the two faces of the fl ag according to Bernoulli’s
theorem, which results fl uttering of fl ag.

5. Assertion(A) : When two boats sails parallel and close to each other, then they are pulled towards
each other.
Reason(R) : Pressure between the boats decreases due to the speed of boats.

Answer key
1. (a), 2. (c), 3. (a), 4. (a), 5. (a)

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