Physics-DPP-1-12.Properties of Matter

PHYSICS Topic: PROPERTIES OF MATTER Date: L 1. Young’s modulus of the material of a wire of length L and radius r is Y N/m2. If the length is reduced to 2 Young’s modulus will be : and radius to r 2 ; the (a) Y (b) 2 Y (c) Y Y 4 (d) 2 2. The bulk modulus of water is 2.1 × 109 N/m2. The pressure required to increase the density of water by 0.1 % is : (a) 2.1 × 103 N/m2 (b) 2.1 × 106 N/m2 (c) 2.1 × 105 N/m2 (d) 2.1 × 107 N/m2 3. A thick rope of rubber of density 1.5 × 103 kg/m3 and Young’s modulus 5 × 106 N/m2, 8 m in length, when hung from ceiling of a room, the increase in length due to its own weight is : (a) 96 × 10–3 m (b) 19.2 × 10–5 m (c) 9.4 cm (d) 9.6 mm 4. A metal block is experiencing an atmoshperic pressure of 105 N/m2. When the same block is placed in a vacuum chamber, the fractional change in its volume : (the bulk modulus of metal is 1.25 × 1011 N/m2) : (a) 4 × 10–7 (b) 2 × 10–7 (c) 8 × 10–7 (d) 1 × 10–7 5. A brass rod of length 2 m and cross-sectional area 2.0 cm2 is attached end to a steel rod of length L and cross-sectional area 1.0 cm2. The compound rod is subjected to equal and opposite pulls of magnitude 5 × 104 N at its ends. If the elongations of the two rods are equal, the length of the steel rod (L) is : Y = 1.0 × 1011 N/m2 and Y = 2.0 × 1011 N/m2) (a) 1.5 m (b) 1.8 m (c) 1 m (d) 2 m 6. An elevator cable is to have a maximum stress of 7 × 107 N/m2 to allow for appropriate safety factors. Its maximum upward acceleration is 1.5 m/s2. If the cable has to support the total weight of 2000 kg of a loaded elevator, the area of cross-section of the cable should be : (a) 3.22 cm2 (b) 2.38 cm2 (c) 0. 32 cm2 (d) 8.23 cm2 7. One end of a uniform wire of length L and weight W is attached rigidly to a point in roof and a weight W1 is suspended from its lower 3L end. If S is the area of cross-section of the wire, the stress in the wire at a height of 4 from its lower end is : çæ 3W ö÷ W1 W W1 + çW1 + ÷ ç W1 + W (a) S (b) 4 S (c) ç S ÷ ç ÷ (d) S çè ø÷ 8. The length of an elastic string is a metre when the tension is 4 N and b metre when the tension is 5 N. The length, in metres, when the tension is 9 N is : (a) (a + b) (b) (4b – 5a) (c) (5 b – 4 a) (d) (9 b – 9a) 9. The length of a metal wire is l1, when the tension in it is T1 and is l2 when the tensionis T2. The unstretched length of the wire is : (a) l1T1 + l2T2 T1 + T2 (b) l1 + l2 2 (c) (c) l1T2 – l2 T1 T2 – T1 (d) (d) l1T2 – l2 T1 T2 + T1 10. A block of weight W produces an extension of 9 cm when it is hung by an elastic spring of length 60 cm and is cut into two parts one of length 40 cm and the other of length 20 cm. The same load W hangs in equilibrium supported by both parts as shown in figure. The extension in cm now is : (a) 9 (b) 6 (c) 3 (d) 2 PHYSICS Topic: PROPERTIES OF MATTER Date: 1. (a) 2. (b) Answer Key 3. (c) 4. (c) 5. (d) 6. (a) 7. (c) 8. (c) 9. (c) 10. (d)