1. An iron rod of length 2m and cross section area of \[50mm^{2}\] , stretched by 0.5 mm, when a mass of 250 kg is hung from its lower end. Young's modulus of
the iron rod is

a) \[19.6 \times 10^{10}N\diagup m^{2}\]

b) \[19.6 \times 10^{15}N\diagup m^{2}\]

c) \[19.6 \times 10^{18}N\diagup m^{2}\]

d) \[19.6 \times 10^{20}N\diagup m^{2}\]

Explanation:

2. In solids, inter-atomic forces are

a) Totally repulsive

b) Totally attractive

c) Combination of (a) and (b)

d) None of these

Explanation: Combination of (a) and (b)

3. A force F is applied on the wire of radius r and length L and change in the length of wire is l. If the same force F is applied on the wire of the
same material and radius 2r and length 2L, Then the change in length of the other wire is

a) l

b) 2l

c) l/2

d) 4l

Explanation:

\[\frac{l}{2}\]

4. The modulus of elasticity is dimensionally equivalent to

a) Surface

b) Stress

c) Strain

d) None of these

Explanation: Stress

5. Under elastic limit the stress is

a) Inversely proportional to strain

b) Directly proportional to strain

c) Square root of strain

d) Independent of strain

Explanation: Directly proportional to strain

6. A load W produces an extension of 1mm in a thread of radius r. Now if the load is made 4W and radius is made 2r all other things remaining
same, the extension will become

a) 4 mm

b) 16 mm

c) 1 mm

d) 0.25 mm

Explanation:

7. The units of Young ‘s modulus of elasticity are

a) \[ N m^{-1}\]

b) N-m

c) \[ N m^{-2}\]

d) \[ N m^{2}\]

Explanation: \[ N m^{-2}\]

8.Two similar wires under the same load yield elongation of 0.1 mm and 0.05 mm respectively. If the area of cross- section of the first wire is
\[ 4mm^{2}\] then the area of cross section of the second wire is

a) \[ 6mm^{2}\]

b) \[ 8mm^{2}\]

c) \[ 10mm^{2}\]

d) \[ 12mm^{2}\]

Explanation:

9. A 5 m long aluminium wire \[\left(Y=7 \times 10^{10}N\diagup m^{2}\right)\] of diameter 3 mm supports a 40 kg mass. In order to
have the same elongation in a copper wire \[\left(Y=12 \times 10^{10}N\diagup m^{2}\right)\] of the same length under the
same weight, the diameter should now be, in mm.

a) 1.75

b) 1.5

c) 2.5

d) 5.0

Explanation:

10. How much force is required to produce an increase of 0.2% in the length of a brass wire of diameter 0.6 mm (Young’s modulus for brass = 0.9 * 10^{11} N/m^{2}
)

a) Nearly 17 N

b) Nearly 34 N

c) Nearly 51 N

d) Nearly 68 N

Explanation: