General
✓✗For streamline flow of an ideal fluid in a horizontal pipe, Bernoulli's equation reduces to
- P = constant
- P + \( \rho \)gh = constant
- Av = constant
- P + (1/2)\( \rho \)v2 = constant
General
✓✗Two bodies of the same material, shape and surface but masses m and 2m are at the same temperature in the same surroundings. Their initial rates of fall of temperature are in the ratio (m : 2m)
- 1 : 1
- 4 : 1
- 2 : 1
- 1 : 2
General
✓✗Stress-strain graphs (straight-line parts) of two wires A and B are drawn with stress on the y-axis. The line for A makes a larger angle with the strain axis than the line for B. Then
- A is more ductile
- both have equal Young's moduli
- A has the larger Young's modulus
- B has the larger Young's modulus
General
✓✗In an experiment, a wire of length 2 m and diameter 0.5 mm gives an extension of 0.4 mm for every 1 kg wt added (g = 10 m s−2). The Young's modulus of the wire is about
- 1.3 × 1011 N m−2
- 5.1 × 1011 N m−2
- 2.5 × 1010 N m−2
- 2.5 × 1011 N m−2
General
✓✗An air bubble of radius r rises steadily through a liquid of density \( \rho \) and viscosity \( \eta \) (air density negligible). Its terminal speed is
- \( \dfrac{r^2\rho g}{9\eta} \)
- \( \dfrac{2r^2\rho g}{3\eta} \)
- \( \dfrac{2r^2\rho g}{9\eta} \)
- \( \dfrac{9r^2\rho g}{2\eta} \)
General
✓✗A hollow sphere is just completely immersed (floating) in water. If its outer volume is V and the material volume is V/4, the density of the material is
- 2 times that of water
- equal to that of water
- 4 times that of water
- 1/4 that of water
General
✓✗Two identical rods conduct heat Q in time t when joined in series between two reservoirs. If they are joined in parallel between the same reservoirs, the heat conducted in the same time is
- Q/2
- Q
- 4Q
- 2Q
General
✓✗Given below are two statements.
Statement I: The Young's modulus of a wire decreases if its length is doubled.
Statement II: Young's modulus depends only on the material (and temperature), not on the dimensions of the wire.
Choose the correct option.
Statement I: The Young's modulus of a wire decreases if its length is doubled.
Statement II: Young's modulus depends only on the material (and temperature), not on the dimensions of the wire.
Choose the correct option.
- Both Statement I and Statement II are correct
- Both Statement I and Statement II are incorrect
- Statement I is correct but Statement II is incorrect
- Statement I is incorrect but Statement II is correct
General
✓✗A wire of length 3 m and area 6 × 10−6 m2 has Y = 1.2 × 1011 N m−2. The force needed to extend it by 1 mm is
- 240 N
- 480 N
- 24 N
- 120 N
General
✓✗Three rods of the same material and area, with lengths in the ratio 1 : 2 : 3, are connected in series. If the total temperature difference is 60°C, the temperature difference across the longest rod is
- 20°C
- 10°C
- 60°C
- 30°C
General
✓✗The temperature at which the Celsius and Fahrenheit scales read the same is
- 100°
- 0°
- 32°
- −40°
General
✓✗Two spherical black bodies of radii r1 and r2 at temperatures T1 and T2 radiate the same power. Then r1/r2 is
- T2/T1
- (T2/T1)2
- (T2/T1)4
- (T1/T2)2
General
✓✗A block of wood floats in water with 2/3 of its volume submerged. In oil it floats with 0.9 of its volume submerged. The density of the oil is
- 900 kg m−3
- 667 kg m−3
- 600 kg m−3
- 741 kg m−3
General
✓✗A light ball held in a vertical jet of air stays suspended in the jet because
- the ball becomes weightless
- the jet has a larger density
- of viscosity alone
- the pressure inside the fast jet is lower than in the surrounding still air
General
✓✗The pressure at the bottom of a lake 20 m deep is (g = 10 m s−2) (atmospheric pressure = 105 Pa)
- 2 × 105 Pa
- 1 × 105 Pa
- 4 × 105 Pa
- 3 × 105 Pa