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

A ball is dropped on a floor from a height of 2.0 m. After the collision it rises up to a height of 1.5 m. Assume that 40% of the mechanical energy lost goes as thermal energy into the ball. Calculate the rise in the temperature of the ball in the collision. Heat capacity of the ball is 800 J K⁻¹.

A ball is dropped on a floor from a height of 2.0 m. After the collision it rises up to a height of 1.5 m. Assume that 40% of the mechanical energy lost goes as thermal energy into the ball. Calculate the rise in the temperature of the ball in the collision. Heat capacity of the ball is 800 J K⁻¹.

A copper cube of mass 200 g slides down on a rough inclined plane of inclination 37° at a constant speed. Assume that any loss in mechanical energy goes into the copper block as thermal energy. Find the increase in the temperature of the block as it slides down through 60 cm. Specific heat capacity of copper = 420 J kg⁻¹ K⁻¹.

A copper cube of mass 200 g slides down on a rough inclined plane of inclination 37° at a constant speed. Assume that any loss in mechanical energy goes into the copper block as thermal energy. Find the increase in the temperature of the block as it slides down through 60 cm. Specific heat capacity of copper = 420 J kg⁻¹ K⁻¹.

Two steel rods and an aluminium rod of equal length l₀ and equal cross-section are joined rigidly at their ends, as shown in the figure below. All the rods are in a state of zero tension at 0°C. Find the length of the system when the temperature is raised to θ. Coefficient of linear expansion of aluminium and steel are α_a and α_s, respectively. Young's modulus of aluminium is Y_a and of steel is Y_s. 

Two steel rods and an aluminium rod of equal length l₀ and equal cross-section are joined rigidly at their ends, as shown in the figure below. All the rods are in a state of zero tension at 0°C. Find the length of the system when the temperature is raised to θ. Coefficient of linear expansion of aluminium and steel are α_a and α_s, respectively. Young's modulus of aluminium is Y_a and of steel is Y_s. 

A metal block of density 600 kg m⁻³ and mass 1.2 kg is suspended through a spring of spring constant 200 N m⁻¹. The spring-block system is dipped in water kept in a vessel. The water has a mass of 260 g and the bloc is at a height 40 cm above the bottom of the vessel. If the support of the spring is broken, what will be the rise in the temperature of the water. Specific heat capacity of the block is 250 J kg⁻³ K⁻¹ and that of water is 4200 J kg⁻¹ K⁻¹. Heat capacities of the vessel and the spring are negligible.

A metal block of density 600 kg m⁻³ and mass 1.2 kg is suspended through a spring of spring constant 200 N m⁻¹. The spring-block system is dipped in water kept in a vessel. The water has a mass of 260 g and the bloc is at a height 40 cm above the bottom of the vessel. If the support of the spring is broken, what will be the rise in the temperature of the water. Specific heat capacity of the block is 250 J kg⁻³ K⁻¹ and that of water is 4200 J kg⁻¹ K⁻¹. Heat capacities of the vessel and the spring are negligible.

A torsional pendulum consists of a solid  disc connected to a thin wire (α = 2.4 × 10^–5°C^–1) at its centre. Find the percentage change in the time period between peak winter (5°C) and peak summer (45°C).
  

A torsional pendulum consists of a solid  disc connected to a thin wire (α = 2.4 × 10^–5°C^–1) at its centre. Find the percentage change in the time period between peak winter (5°C) and peak summer (45°C).
  

A circular disc made of iron is rotated about its axis at a constant velocity ω. Calculate the percentage change in the linear speed of a particle of the rim as the disc is slowly heated from 20°C to 50°C, keeping the angular velocity constant. Coefficient of linear expansion of iron = 1.2 × 10^–5 °C^–1.

A circular disc made of iron is rotated about its axis at a constant velocity ω. Calculate the percentage change in the linear speed of a particle of the rim as the disc is slowly heated from 20°C to 50°C, keeping the angular velocity constant. Coefficient of linear expansion of iron = 1.2 × 10^–5 °C^–1.

50 m³ of saturated vapour is cooled down from 30°C to 20°C. Find the mass of the water condensed. The absolute humidity of saturated water vapour is 30 g m⁻³ at 30°C and 16 g m⁻³ at 20°C.

Estimate the average thermal energy of a helium atom at room temperature (27 °C).

Estimate the average thermal energy of a helium atom at the temperature on the surface of the Sun (6000 K).

Three vessels of equal capacity have gases at the same temperature and pressure. The first vessel contains neon (monatomic), the second contains chlorine (diatomic), and the third contains uranium hexafluoride (polyatomic).

Do the vessels contain an equal number of respective molecules?

The transverse displacement of a string (clamped at its both ends) is given by

y(x, t) = 0.06 sin `2/3` x cos (120 πt)

where x and y are in m and t in s. The length of the string is 1.5 m and its mass is 3.0 × 10^-2 kg.

Answer the following:

Does the function represent a travelling wave or a stationary wave?

The transverse displacement of a string (clamped at its both ends) is given by

y(x, t) = 0.06 sin `2/3` x cos (120 πt)

where x and y are in m and t in s. The length of the string is 1.5 m and its mass is 3.0 × 10^-2 kg.

Answer the following:

Interpret the wave as a superposition of two waves travelling in opposite
directions. What is the wavelength, frequency, and speed of each wave?

If |A| = 2 and |B| = 4, then match the relations in column I with the angle θ between A and B in column II

In figure, a body A of mass m slides on plane inclined at angle θ₁ to the horizontal and µ₁ is the coefficent of friction between A and the plane. A is connected by a light string passing over a frictionless pulley to another body B, also of mass m, sliding on a frictionless plane inclined at angle θ₂ to the horizontal. Which of the following statements are true?

1. A will never move up the plane.
2. A will just start moving up the plane when `µ = (sin  θ_2 - sin  θ_1)/(cos  θ_1)`
3. For A to move up the plane, θ₂ must always be greater than θ₁.
4. B will always slide down with constant speed.