NCERT Physics Class 11 Exemplar Ch 9 Mechanical Properties of Solids Part 1

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Q.1 Modulus of rigidity of ideal liquids is

(a) infinity.

(b) zero.

(c) unity.

(d) some finite small non-zero constant value.

Answer: (b)

Q.2 The maximum load a wire can withstand without breaking, when its length is reduced to half of its original length, will

(a) be double.

(b) behalf.

(c) be four times.

(d) remain same.

Answer: (d)

Q.3 The temperature of a wire is doubled. The Young’s modulus of elasticity

(a) will also double.

(b) will become four times.

(c) will remain same.

(d) will decrease.

Answer: (d)

Q.4 A spring is stretched by applying a load to its free end. The strain produced in the spring is

(a) volumetric.

(b) shear.

(c) longitudinal and shear.

(d) longitudinal.

Answer: (c)

Q.5 A rigid bar of mass M is supported symmetrically by three wires each of length Those at each end are of copper and the middle one is of iron. The ratio of their diameters, if each is to have the same tension, is equal to

(a)

(b)

(c)

(d)

Answer: (b)

Q.6 A mild steel wire of length 2L and cross-sectional area A is stretched, well within elastic limit, horizontally between two pillars (Fig. 9.1). A mass m is suspended from the midpoint of the wire. Strain in the wire is

Block suspended by string

Block Suspended by String

Block suspended by string

Answer: (a)

Q. 7 A rectangular frame is to be suspended symmetrically by two strings of equal length on two supports (Fig). It can be done in one of the following three ways;

Rectangular frame suspended by string

Rectangular Frame Suspended by String

Rectangular frame suspended by string

The tension in the strings will be

(a) the same in all cases.

(b) least in (a).

(c) least in (b).

(d) least in (c).

Answer: (c)

Q. 8 Consider two cylindrical rods of identical dimensions, one of rubber and the other of steel. Both the rods are fixed rigidly at one end to the roof. A mass M is attached to each of the free ends at the centre of the rods.

(a) Both the rods will elongate but there shall be no perceptible change in shape.

(b) The steel rod will elongate and change shape but the rubber rod will only elongate.

(c) The steel rod will elongate without any perceptible change in shape, but the rubber rod will elongate and the shape of the bottom edge will change to an ellipse.

(d) The steel rod will elongate, without any perceptible change in shape, but the rubber rod will elongate with the shape of the bottom edge tapered to a tip at the centre

Answer: (d)

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