1. A uniform plank of Young’s modulus Y is moved over a smooth horizontal surface by a constant
horizontal force F. The area of cross section of the plank is A. The compressive strain on the plank in the direction of the force is

a) \[F\diagup AY\]

b) \[2F\diagup AY\]

c) \[\frac{1}{2}\left(F\diagup AY\right)\]

d) \[3F\diagup AY\]

Explanation:

2.The mean distance between the atoms of iron is \[3\times 10^{-10}m\] and interatomic force constant for iron
is 7 N/m The Young’s modulus of elasticity for iron is

a) \[2.33\times 10^{5}N\diagup m^{2}\]

b) \[23.3\times 10^{10}N\diagup m^{2}\]

c) \[233\times 10^{10}N\diagup m^{2}\]

d) \[2.33\times 10^{10}N\diagup m^{2}\]

Explanation:

3. Two wires A and B are of same materials. Their lengths are in the ratio 1 : 2 and diameters are in the ratio 2 : 1 when stretched by force F_{A} and F_{B} respectively they get equal increase in their
lengths. Then the ratio \[F_{A}\diagup F_{B}\] should be

a) 1 : 2

b) 1 : 1

c) 2 : 1

d) 8 : 1

Explanation:

4. The breaking stress of a wire depends upon

a) Length of the wire

b) Radius of the wire

c) Material of the wire

d) Shape of the cross section

Explanation: Material of the wire

5. The area of cross section of a steel wire \[\left(Y=2.0\times 10^{11}N\diagup m^{2}\right)\] is 0.1 cm^{2}. The force required
to double its length will be

a) \[2\times 10^{12}N\]

b) \[2\times 10^{11}N\]

c) \[2\times 10^{10}N\]

d) \[2\times 10^{6}N\]

Explanation:

6. A rubber cord catapult has cross-sectional area \[25 m m^{2}\] and initial length of rubber cord is 10 cm. It is stretched to 5 cm. and then released to project a
missile of mass 5 gm. Taking \[Y_{rubber}=5\times 10^{8}N\diagup m^{2}\] . velocity of projected missile is

a) \[20 ms^{-1}\]

b) \[100 ms^{-1}\]

c) \[250 ms^{-1}\]

d) \[200 ms^{-1}\]

Explanation: Potential energy stored in the rubber cord catapult will be converted into kinetic energy of mass.

7. According to Hook’s law force is proportional to

a) \[\frac{1}{x}\]

b) \[\frac{1}{x^{2}}\]

c) x

d) \[x^{2}\]

Explanation: According to Hook’s law force is proportional to x

8. In the Young’s experiment, If length of wire and radius both are doubled then the value of Y will
become

a) 2 times

b) 4 times

c) Remains same

d) Half

Explanation: Remains same

9. Minimum and maximum values of Poisson’s ratio for a metal lies between

a) \[-\infty\] to \[+\infty\]

b) 0 to 1

c) \[-\infty\] to 1

d) 0 to 0.5

Explanation: 0 to 0.5

10.A wire of diameter 1mm breaks under a tension of 1000 N. Another wire, of same material as that of the first one, but of diameter 2 mm breaks
under a tension of

a) 500 N

b) 1000 N

c) 10000 N

d) 4000 N

Explanation: Breaking force \[\propto\] r

^{2}

If diameter becomes double then breaking force will become four times i.e. 1000 × 4 = 4000 N