Practice Paper
TERM II (2021 – 2022)
Class – XI
Physics
Time: 2 hours Maximum Marks: 35
General Instructions:
(i) There are 12 questions in all. All questions are compulsory.
(ii) This question paper has three sections: Section A, Section B and Section C.
(iii) Section A contains three questions of two marks each, Section B contains eight questions of three marks each; Section C contains one case study-based question of five marks.
(iv) There is no overall choice. However, an internal choice has been provided in one question of two marks and two questions of three marks. You have to attempt only one of the choices in such questions.
(v) You may use log tables if necessary but use of calculator is not allowed.
SECTION – A
- Derive the expression for excess pressure inside a liquid drop.
- The opposite faces of a cubical block of iron of cross-section 4 cm2 are kept in contact with steam and melting ice. Calculate the amount of ice melted at the end of 10 minutes if K = 0.2 cal cm-1 s-1 °c-1 for iron. Latent heat of fusion of ice = 80 cal g-1
OR
A circular hole of a radius of 1 cm is drilled in a brass sheet kept at 293K. What will be the diameter of the hole when the sheet is heated to 393K? α for brass =18 × 10-6 K-1.
3. The temperature of the gas in Kelvin is made 9 times. How does it affect the total K.E., average K.E., r.m.s velocity and pressure?
SECTION – B
4. Two exactly similar wires of steel and copper are stretched by equal forces. If the total elongation is 1 cm, find by how much each wire is elongated. Given Y for steel = 20 × 1011 dyne cm-2, Y for copper = 12 × 1011 dyne cm-2
OR
If B be the bulk modulus of a metal and a pressure P is applied uniformly on all its sides. If D be the density of metal, then find the fractional increase in its density.
5. Answer the following:
(a) The triple-point of water is a standard fixed point in modern thermometry. Why? What is wrong in taking the melting point of ice and the boiling point of water as standard fixed points (as was originally done in the Celsius scale)?
(b) There were two fixed points in the original Celsius scale as mentioned above which were assigned the number 0°C and 100°C respectively. On the absolute scale, one of the fixed points is the triple-point of water, which on the Kelvin absolute scale is assigned the number 273.16 K. What is the other fixed point on this (Kelvin) Scale?
(c) The absolute temperature (Kelvin scale) T is related to the temperature tc on the Celsius scale tc = T – 273.15
6. Derive the expression for the work done during:
(a) Isothermal process
(b) Adiabatic process
7. A 50g lead bullet (specific heat 0.02) is initially at 30°C. It is fired vertically upward with a speed of 840 ms-1. On returning to the starting level, it strikes a cake of ice at 0°C. How much ice is melted? Assume that all energy is spent in melting only. Latent heat of ice = 80 cal g-1.
8. Show that for a particle in linear SHM the average kinetic energy over a period of oscillation equals the average potential energy over the same period.
9. A harmonic oscillation is represented by y = 0.34 cos (3000 t + 0.74) where y and t are in cm and s respectively. Deduce
(i) amplitude,
(ii) frequency and angular frequency,
(iii) time period,
(iv) initial phase.
10. Derive expressions for apparent frequency when
(i) source is moving towards an observer at rest.
(ii) the observer is moving towards the source at rest.
(iii) both source and observer are in motion towards each other.
11. Explain why (or how):
(a) in a sound wave, a displacement node is a pressure antinode and vice versa.
(b) Bats can ascertain distances, directions, nature and sizes of the obstacles without any “eyes”.
(c) A violin note and sitar note may have the same frequency, yet we can distinguish between the two notes.
OR
What are the characteristics of wave motion?
Distinguish between stationary and progressive waves
SECTION C
12. Bernoulli’s Principle:
It states that sum of pressure energy, kinetic energy and potential energy per unit volume of an incompressible, non-viscous fluid in a streamlined, rotational flow remains constant along a streamline.
m = volume x density
m = area of cross-section x length x density
At area of cross section A1 = a1 v1 ∆t ρ = a1 v1 ∆t ρ
At area of cross section A2 = a2 v2 ∆t ρ = a2 v2 ∆t ρ
a1 v1 = a2 v2 …… (i)
change in K.E. of fluid = K.E. at B – K.E. at A
= ½ m (v22 -v12)
= ½ a1 v1 ∆t ρ (v22 -v12)
change in P.E. of fluid = mg (h2– h1)
= P.E. at B – P.E. at A
= a1 v1 ∆t ρ g (h2– h1)
Net work done (F.S) on the fluid
= work done on fluid at A – Work done on fluid at B
= P1 a1 x v1 ∆t – P2 a2 x v2 ∆t
= a1 v1 ∆t (P1 – P2)
According to law of conservation of energy
Net work done on fluid = Change in KE + change in PE
a1 v1∆t (P1 – P2) = ½ a1v1∆t ρ(v22 – v12) + a1v1∆t ρ g(h2 – h1)
Dividing both side by a1 v1 ∆t, we get
(P1 – P2) = ½ ρ(v22 -v12) + ρ g (h2 – h1)
P1 + ½ ρv12+ ρ g h1 = P2 + ½ ρv22 + ρ g h2
P+ ½ ρv2+ ρ g h= constant
(i) Bernoulli’ s equation is applied to
- venturi mrter
- Orifice meter
- Lifting of aeroplane
- All of the above
(ii) Bernoulli’ s principle is based on conservation of
- Mass
- Energy
- Momentum
- None of the above
(iii) Bernoulli’s equation holds only for
- Low viscosity and incompressible fluids in turbulent flow
- high viscosity and incompressible fluids in streamline flow
- Low viscosity and compressible fluids in turbulent flow
- Low viscosity and incompressible fluids in streamline flow
(iv) If the flow speeds of the upper and lower of the wings of an aeroplane are 260 m/s and 250 m/s, the wings cover an area of 500 m2, then what would be the lift generated in kN?
- 637.5
- 1275
- 2550
- 350
(v) Consider a tank of height 20 m filled with liquid of density 100kg/ m3. The area of tank is 10 m2. If the tank has a hole of area 2 m2 at the bottom, find the speed of the liquid flowing out through the hole when the height of liquid in the tank is 10 m. Assume speed of liquid descending at top of tank is 5 m/s.
- 20 m/s
- 14.14 m/s
- 15 m/s
- 20.615 m/s