Page 100 - Physics - XI

COMPETENCY-BASED QUESTIONS
COMPETENCY-BASED QUESTIONS

Multiple Choice Questions

Q1. Dimensions of stress are
a. [ML T ] b. [ML T ] c. [ML T ] d. [MLT ]
–2
2
–2
–1
–2
–1
0
Q2. The normal density of a material is ρ and its bulk modulus is K. The magnitude of increase in
density of material when a pressure P is applied uniformly on all sides will be
a. K b. PK c. ρP d. ρK
ρ P ρ K P
Q3. A wire of length L and area of cross-section A is hanging from a fi xed support. The length of
the wire change to L when mass M is suspended from its free end. The expression for Young's
1
modulus is

MgL MgL Mg L( − L) MgL
a. b. c. 1 d. 1
AL 1 AL( 1 − L) AL AL
Q4. If the ratio of diameters, lengths, and Young's modulus of steel and copper wires shown in
the fi gure are p, q, and s respectively, then the corresponding ratio of increase in their lengths
would be

5q 7q Steel
a. b.
2
2
( 7sp ) ( 5sp ) 2 m
2q 7q
c. d. Copper
( 5sp) ( 5sp)

5 m

Q5. The Young's modulus of steel is twice that of brass. Two wires of same length and of same area
of cross section, one of steel and another of brass are suspended from the same roof. If we want
the lower ends of the wires to be at the same level, then the weights added to the steel and brass
wires must be in the ratio of

a. 4 : 1 b. 1 : 1 c. 1 : 2 d. 2 : 1
Q6. A rod of length L at room temperature and uniform area of cross section A is made of a
metal having coeffi cient of linear expansion α/°C. It is observed that an external compressive
force F is applied on each of its ends, prevents any change in the length of the rod when its
temperature rises by ∆T.K. Young's modulus Y for this metal is

2F F F F
a. b. c. d.
T
A T A ( 273 ) A T 2 A T
Q7. A man grows into a giant such that his linear dimensions increase by a factor of 9. Assuming
that his density remains same, the stress in the leg will change by a factor of

a. 1 b. 81 c. 1 d. 9
9 81

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