Science (English Medium) इयत्ता ११ - CBSE Question Bank Solutions for Physics

Show the nature of the following graph for a satellite orbiting the earth. 

1. KE vs orbital radius R
2. PE vs orbital radius R
3. TE vs orbital radius R.

Why does a metal bar appear hotter than a wooden bar at the same temperature? Equivalently it also appears cooler than wooden bar if they are both colder than room temperature.

Consider a heat engine as shown in figure Q₁ and Q₂ are heat added to heat bath T₁ and heat taken from T₂ in one cycle of engine. W is the mechanical work done on the engine. If W > 0, then possibilities are ______.

1. Q₁ > Q₂ > 0
2. Q₂ > Q₁ > 0
3. Q₂ < Q₁ < 0
4. Q₁ < 0, Q₂ > 0

If a refrigerator’s door is kept open, will the room become cool or hot? Explain.

If the co-efficient of performance of a refrigerator is 5 and operates at the room temperature (27°C), find the temperature inside the refrigerator.

Calculate the ratio of the mean free paths of the molecules of two gases having molecular diameters 1 A and 2 A. The gases may be considered under identical conditions of temperature, pressure and volume.

Ten small planes are flying at a speed of 150 km/h in total darkness in an air space that is 20 × 20 × 1.5 km³ in volume. You are in one of the planes, flying at random within this space with no way of knowing where the other planes are. On the average about how long a time will elapse between near collision with your plane. Assume for this rough computation that a saftey region around the plane can be approximated by a sphere of radius 10 m.

Four pendulums A, B, C and D are suspended from the same elastic support as shown in figure. A and C are of the same length, while B is smaller than A and D is larger than A. If A is given a transverse displacement ______.

With propagation of longitudinal waves through a medium, the quantity transmitted is ______.

Which of the following statements are true for wave motion?

Equation of a plane progressive wave is given by `y = 0.6 sin 2π (t - x/2)`. On reflection from a denser medium its amplitude becomes 2/3 of the amplitude of the incident wave. The equation of the reflected wave is ______.

During propagation of a plane progressive mechanical wave ______.

1. all the particles are vibrating in the same phase.
2. amplitude of all the particles is equal.
3. particles of the medium executes S.H.M.
4. wave velocity depends upon the nature of the medium.

The speed-time graph of a particle moving along a fixed direction is shown in Fig. 3.28. Obtain the distance traversed by the particle between (a) t = 0 s to 10 s, (b) t = 2 s to 6 s.

What is the average speed of the particle over the intervals in (a) and (b)

The velocity-time graph of a particle in one-dimensional motion is shown in Figure

Which of the following formulae are correct for describing the motion of the particle over the time-interval t₂ to t₁?

(a) x(t₂) = x(t₁) + v(t₁)(t₂–t₁) + (1/2)a(t₂–t₁)²

(b) v(t₂)= v(t₁) + a(t₂–t₁)

(c) v_Average = (x(t₂) – x(t₁)) / (t₂ – t₁)

(d) a_Average = (v(t₂) – v(t₁)) / (t₂ – t₁)

(e) x(t₂) = x(t₁) + v_Average(t₂ – t₁) + (1/2)a_Average(t₂ – t₁)²

(f) x(t₂) – x(t₁) = area under the v–t curve bounded by the t-axis and the dotted line shown.

Choose the correct alternative:

If the zero of potential energy is at infinity, the total energy of an orbiting satellite is negative of its kinetic/potential energy.

Choose the correct alternative:

The energy required to launch an orbiting satellite out of earth’s gravitational influence is more/less than the energy required to project a stationary object at the same height (as the satellite) out of earth’s influence.

A satellite orbits the earth at a height of 400 km above the surface. How much energy must be expended to rocket the satellite out of the earth’s gravitational influence? Mass of the satellite = 200 kg; mass of the earth = 6.0 ×10²⁴ kg; radius of the earth = 6.4 ×10⁶ m; G = 6.67 × 10^–11 N m² kg^–2

A body is moving unidirectionally under the influence of a source of constant power. Its displacement in time t is proportional to ______.

A pump on the ground floor of a building can pump up water to fill a tank of volume 30 m³ in 15 min. If the tank is 40 m above the ground, and the efficiency of the pump is 30%, how much electric power is consumed by the pump?

The blades of a windmill sweep out a circle of area A.

1. If the wind flows at a velocity v perpendicular to the circle, what is the mass of the air passing through it in time t?
2. What is the kinetic energy of the air?
3. Assume that the windmill converts 25% of the wind’s energy into electrical energy, and that A = 30 m², v = 36 km/h and the density of air is 1.2 kg m^–3. What is the electrical power produced?