9th class Physics, Chapter 6: Mechanical Properties of Matter MCQs

1. A wire is stretched by a weight w. If the diameter of the wire is reduced to half of its previous value, the extension will become:

1. (A) one half
2. (B) double
3. (C) one fourth
4. (D) four times ✓

2. Four wires of the same material are stretched by the same load. Their dimensions are given below. Which of them will elongate most?

1. (A) Length 1 m, diameter 1 mm
2. (B) Length 2 m, diameter 2 mm
3. (C) Length 3 m, diameter 3 mm
4. (D) Length 4 m, diameter 0.5 mm ✓

3. Two metal plates of area 2 and 3 square metres are placed in a liquid at the same depth. The ratio of pressures on the two plates is:

1. (A) 1 : 1 ✓
2. (B) √2 : √3
3. (C) 2 : 3
4. (D) 4 : 9

4. The pressure at any point in a liquid is proportional to:

1. (A) density of the liquid
2. (B) depth of the point below the surface of the liquid
3. (C) acceleration due to gravity
4. (D) all of the above ✓

5. Pressure applied to an enclosed fluid is:

1. (A) increased and applied to every part of the fluid
2. (B) diminished and transmitted to the walls of container
3. (C) increased in proportion to the mass of fluid and then transmitted to each part of the fluid
4. (D) transmitted unchanged to every portion of the fluid and walls of containing vessel ✓

6. The principle of a hydraulic press is based on:

1. (A) Hooke's law
2. (B) Pascal's law ✓
3. (C) Principle of conservation of energy
4. (D) Principle of conservation of momentum

7. When a spring is compressed, what form of energy does it possess?

1. (A) Kinetic
2. (B) Potential ✓
3. (C) Internal
4. (D) Heat

8. What is the force exerted by the atmosphere on a rectangular block surface of length 50 cm and breadth 40 cm? The atmospheric pressure is 100 kPa.

1. (A) 20 kN ✓
2. (B) 100 kN
3. (C) 200 kN
4. (D) 500 kN

9. A force that changes the size or shape of an object is called a:

1. (A) deforming force ✓
2. (B) restoring force
3. (C) balanced force
4. (D) frictional force

10. An object is said to be elastic if, after removal of the deforming force, it:

1. (A) restores its original size and shape ✓
2. (B) remains deformed
3. (C) breaks
4. (D) becomes harder

11. The limit up to which a material regains its original shape is called the:

1. (A) elastic limit ✓
2. (B) breaking point
3. (C) melting point
4. (D) density limit

12. Beyond the elastic limit, the change in the material becomes:

1. (A) permanent ✓
2. (B) temporary
3. (C) zero
4. (D) smaller

13. Which of the following materials is inelastic?

1. (A) Rubber band
2. (B) Tennis racket string
3. (C) Plasticine ✓
4. (D) Steel spring

14. According to Hooke's law, within the elastic limit the extension of a spring is:

1. (A) proportional to the square of the force
2. (B) directly proportional to the applied force ✓
3. (C) inversely proportional to the applied force
4. (D) independent of the force

15. The formula for Hooke's law is:

1. (A) F = k / x
2. (B) F = k x²
3. (C) F = x / k
4. (D) F = k x ✓

16. The SI unit of spring constant is:

1. (A) N m
2. (B) N
3. (C) N m⁻²
4. (D) N m⁻¹ ✓

17. The spring constant is a measure of the:

1. (A) density of the spring
2. (B) mass of the spring
3. (C) length of the spring
4. (D) stiffness of the spring ✓

18. The graph of force against extension of a spring within the elastic limit is:

1. (A) a circle
2. (B) a straight line through the origin ✓
3. (C) a curve
4. (D) a horizontal line

19. The gradient (slope) of a force-extension graph gives the:

1. (A) density
2. (B) pressure
3. (C) spring constant ✓
4. (D) work done

20. A spring is stretched 5 cm by a force of 10 N. Its spring constant is:

1. (A) 50 N m⁻¹
2. (B) 0.5 N m⁻¹
3. (C) 200 N m⁻¹ ✓
4. (D) 2 N m⁻¹