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

The net external torque on a system of particles about an axis is zero. Which of the following are compatible with it?

1. The forces may be acting radially from a point on the axis.
2. The forces may be acting on the axis of rotation.
3. The forces may be acting parallel to the axis of rotation.
4. The torque caused by some forces may be equal and opposite to that caused by other forces.

A uniform cube of mass m and side a is placed on a frictionless horizontal surface. A vertical force F is applied to the edge as shown in figure. Match the following (most appropriate choice):

A uniform sphere of mass m and radius R is placed on a rough horizontal surface (Figure). The sphere is struck horizontally at a height h from the floor. Match the following:

A door is hinged at one end and is free to rotate about a vertical axis (Figure). Does its weight cause any torque about this axis? Give reason for your answer.

Two discs of moments of inertia I₁ and I₂ about their respective axes (normal to the disc and passing through the centre), and rotating with angular speed ω₂ and ω₂ are brought into contact face to face with their axes of rotation coincident.

1. Does the law of conservation of angular momentum apply to the situation? why?
2. Find the angular speed of the two-disc system.
3. Calculate the loss in kinetic energy of the system in the process.
4. Account for this loss.

If p₀ = 1.03 × 10⁵ Nm^–2, ρ₀ = 1.29 kg m^–3 and g = 9.8 ms^–2, at what height will the pressure drop to (1/10) the value at the surface of the earth?

Mark the correct options:

1. A system X is in thermal equilibrium with Y but not with Z. System Y and Z may be in thermal equilibrium with each other.
2. A system X is in thermal equilibrium with Y but not with Z. Systems Y and Z are not in thermal equilibrium with each other.
3. A system X is neither in thermal equilibrium with Y nor with Z. The systems Y and Z must be in thermal equilibrium with each other.
4. A system X is neither in thermal equilibrium with Y nor with Z. The system Y and Z may be in thermal equilibrium with each other.

During summers in India, one of the common practice to keep cool is to make ice balls of crushed ice, dip it in flavoured sugar syrup and sip it. For this a stick is inserted into crushed ice and is squeezed in the palm to make it into the ball. Equivalently in winter, in those areas where it snows, people make snow balls and throw around. Explain the formation of ball out of crushed ice or snow in the light of P–T diagram of water.

100 g of water is supercooled to –10°C. At this point, due to some disturbance mechanised or otherwise some of it suddenly freezes to ice. What will be the temperature of the resultant mixture and how much mass would freeze?

`[S_w = 1cal/g/^circC and L_(Fusion)^w = 80cal/g]`

Consider P-V diagram for an ideal gas shown in figure.

Out of the following diagrams (figure), which represents the T-P diagram?

(i)	(ii)
(iii)	(iv)

A gas mixture consists of 2.0 moles of oxygen and 4.0 moles of neon at temperature T. Neglecting all vibrational modes, calculate the total internal energy of the system. (Oxygen has two rotational modes.)

Explain why there is fall in temperature with altitude.

The relation between acceleration and displacement of four particles are given below: Which one of the particles is executing simple harmonic motion?

A particle executing S.H.M. has a maximum speed of 30 cm/s and a maximum acceleration of 60 cm/s². The period of oscillation is ______.

Which of the following statements is/are true for a simple harmonic oscillator?

1. Force acting is directly proportional to displacement from the mean position and opposite to it.
2. Motion is periodic.
3. Acceleration of the oscillator is constant.
4. The velocity is periodic.

Two identical springs of spring constant K are attached to a block of mass m and to fixed supports as shown in figure. When the mass is displaced from equilibrium position by a distance x towards right, find the restoring force

When will the motion of a simple pendulum be simple harmonic?

The length of a second’s pendulum on the surface of earth is 1 m. What will be the length of a second’s pendulum on the moon?

Find the time period of mass M when displaced from its equilibrium position and then released for the system shown in figure.

A body of mass m is situated in a potential field U(x) = U₀ (1 – cos αx) when U₀ and α are constants. Find the time period of small oscillations.