Unit – 7 : Properties of Matter (Multiple Choice Questions)

1. Consider two wires X and Y. The radius of wire X is 3 times the radius of Y. If they are stretched by the same load, then the stress on Y is

a) equal to that on X
b) thrice that on X
c) nine times that on X
d) half that on X
Answer: c)

2. If a wire is stretched to double of its original length, then the strain in the wire is

a) 1
b) 2
c) 3
d) 4
Answer: a)

3. The load–elongation graph of three wires of the same material is shown. Which of the following wire is the thickest?

Load elongation graph for three wires
a) wire 1
b) wire 2
c) wire 3
d) all have same thickness
Answer: a)

4. For a given material, the rigidity modulus is $\frac{1}{3}$ of Young’s modulus. Its Poisson’s ratio is

a) 0
b) 0.25
c) 0.3
d) 0.5
Answer: d)

5. A small sphere of radius 2 cm falls in a viscous liquid. The rate of production of heat when it attains terminal velocity is proportional to

a) $2^2$
b) $2^3$
c) $2^4$
d) $2^5$
Answer: d)

6. Two wires of same material and same volume have cross-sectional areas $A$ and $2A$. If force $F$ produces extension $\Delta l$ in the first wire, the force needed for same extension in second wire is

a) $2F$
b) $4F$
c) $8F$
d) $16F$
Answer: b)

7. With an increase in temperature, the viscosity of liquid and gas respectively will

a) increase, increase
b) increase, decrease
c) decrease, increase
d) decrease, decrease
Answer: c)

8. The Young’s modulus for a perfectly rigid body is

a) 0
b) 1
c) 0.5
d) infinity
Answer: d)

9. Which of the following is not a scalar?

a) viscosity
b) surface tension
c) pressure
d) stress
Answer: d)

10. If the temperature of a wire is increased, then the Young’s modulus will

a) remain same
b) decrease
c) increase rapidly
d) increase by very small amount
Answer: b)

11. Copper of volume $V$ is drawn into a wire of length $l$. If force $F$ produces extension $\Delta l$, which graph is a straight line?

a) $\Delta l$ vs $V$
b) $\Delta l$ vs $Y$
c) $\Delta l$ vs $F$
d) $\Delta l$ vs $\frac{1}{l}$
Answer: c)

12. Spherical drops of radius $r$ combine to form one drop of radius $R$. If $T$ is surface tension, then

a) $4VT\left(\frac1r-\frac1R\right)$ released
b) $3VT\left(\frac1r+\frac1R\right)$ absorbed
c) $3VT\left(\frac1r-\frac1R\right)$ released
d) no energy change
Answer: c)

13. Four wires of same material are subjected to same tension. Which has maximum extension?

a) length 200 cm, diameter 0.5 mm
b) length 200 cm, diameter 1 mm
c) length 200 cm, diameter 2 mm
d) length 200 cm, diameter 3 mm
Answer: a)

14. Wettability of a surface by a liquid depends primarily on

a) viscosity
b) surface tension
c) density
d) angle of contact
Answer: d)

15. In a horizontal pipe of non-uniform cross-section, water flows at $1~ms^{-1}$ where diameter is 20 cm. The speed at point where diameter is 5 cm is

a) 8
b) 16
c) 24
d) 32
Answer: b)