Science (English Medium) Class 11 - CBSE Question Bank Solutions

A uniform square plate has a small piece Q of an irregular shape removed and glued to the centre of the plate leaving a hole behind (Figure). The moment of inertia about the z-axis is then ______.

With reference to figure of a cube of edge a and mass m, state whether the following are true or false. (O is the centre of the cube.)

1. The moment of inertia of cube about z-axis is Iz = Ix + Iy
2. The moment of inertia of cube about z ′ is I'z = `I_z + (ma^2)/2`
3. The moment of inertia of cube about z″ is = `I_z + (ma^2)/2`
4. I_x = I_y

Why does a solid sphere have smaller moment of inertia than a hollow cylinder of same mass and radius, about an axis passing through their axes of symmetry?

Satellites orbiting the earth have finite life and sometimes debris of satellites fall to the earth. This is because ______.

Is it possibe for a body to have inertia but no weight?

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.