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

If momentum (P), area (A) and time (T) are taken to be fundamental quantities, then energy has the dimensional formula ______.

The displacement of a progressive wave is represented by y = A sin(ωt – kx), where x is distance and t is time. Write the dimensional formula of (i) ω and (ii) k.

In Figure, the co-efficient of friction between the floor and the body B is 0.1. The co-efficient of friction between the bodies B and A is 0.2. A force F is applied as shown on B. The mass of A is m /2 and of B is m. Which of the following statements are true?

1. The bodies will move together if F = 0.25 mg.
2. The body A will slip with respect to B if F = 0.5 mg.
3. The bodies will move together if F = 0.5 mg.
4. The bodies will be at rest if F = 0.1 mg.
5. The maximum value of F for which the two bodies will move together is 0.45 mg.

Mass m₁ moves on a slope making an angle θ with the horizontal and is attached to mass m₂ by a string passing over a frictionless pulley as shown in figure. The coefficient of friction between m₁ and the sloping surface is µ.

1. If m₂ > m₁ sin θ, the body will move up the plane.
2. If m₂ > m₁ (sin θ + µ cos θ), the body will move up the plane.
3. If m₂ < m₁ (sin θ + µ cos θ), the body will move up the plane.
4. If m₂ < m₁ (sin θ − µ cos θ), the body will move down the plane.

Why are mountain roads generally made winding upwards rather than going straight up?

Two masses of 5 kg and 3 kg are suspended with help of massless inextensible strings as shown in figure. Calculate T₁ and T₂ when whole system is going upwards with acceleration = 2 ms² (use g = 9.8 ms^–2).

A block of mass M is held against a rough vertical wall by pressing it with a finger. If the coefficient of friction between the block and the wall is µ and the acceleration due to gravity is g, calculate the minimum force required to be applied by the finger to hold the block against the wall?

A person in an elevator accelerating upwards with an acceleration of 2 ms^–2, tosses a coin vertically upwards with a speed of 20 ms¹. After how much time will the coin fall back into his hand? ( g = 10 ms^–2)

A rectangular box lies on a rough inclined surface. The co-efficient of friction between the surface and the box is µ. Let the mass of the box be m.

1. At what angle of inclination θ of the plane to the horizontal will the box just start to slide down the plane?
2. What is the force acting on the box down the plane, if the angle of inclination of the plane is increased to α > θ ?
3. What is the force needed to be applied upwards along the plane to make the box either remain stationary or just move up with uniform speed?
4. What is the force needed to be applied upwards along the plane to make the box move up the plane with acceleration a?

The potential energy function for a particle executing linear SHM is given by `V(x) = 1/2 kx^2` where k is the force constant of the oscillator (Figure). For k = 0.5 N/m, the graph of V(x) versus x is shown in the figure. A particle of total energy E turns back when it reaches `x = ±x_m`. If V and K indicate the P.E. and K.E., respectively of the particle at `x = +x_m`, then which of the following is correct?

A body is moved along a closed loop. Is the work done in moving the body necessarily zero? If not, state the condition under which work done over a closed path is always zero.

An engine is attached to a wagon through a shock absorber of length 1.5 m. The system with a total mass of 50,000 kg is moving with a speed of 36 km h^–1 when the brakes are applied to bring it to rest. In the process of the system being brought to rest, the spring of the shock absorber gets compressed by 1.0 m. If 90% of energy of the wagon is lost due to friction, calculate the spring constant.

A curved surface is shown in figure. The portion BCD is free of friction. There are three spherical balls of identical radii and masses. Balls are released from rest one by one from A which is at a slightly greater height than C.

With the surface AB, ball 1 has large enough friction to cause rolling down without slipping; ball 2 has a small friction and ball 3 has a negligible friction.

1. For which balls is total mechanical energy conserved?
2. Which ball (s) can reach D?
3. For balls which do not reach D, which of the balls can reach back A?

Two identical steel cubes (masses 50 g, side 1 cm) collide head-on face to face with a speed of 10 cm/s each. Find the maximum compression of each. Young’s modulus for steel = Y = 2 × 10¹¹ N/m².

The centre of gravity of a body on the earth coincides with its centre of mass for a ‘small’ object whereas for an ‘extended’ object it may not. What is the qualitative meaning of ‘small’ and ‘extended’ in this regard? For which of the following the two coincides? A building, a pond, a lake, a mountain?

The vector sum of a system of non-collinear forces acting on a rigid body is given to be non-zero. If the vector sum of all the torques due to the system of forces about a certain point is found to be zero, does this mean that it is necessarily zero about any arbitrary point?

For an ideal liquid ______.

1. the bulk modulus is infinite.
2. the bulk modulus is zero. 
3. the shear modulus is infinite.
4. the shear modulus is zero.

For an ideal liquid ______.

1. the bulk modulus is infinite.
2. the bulk modulus is zero. 
3. the shear modulus is infinite.
4. the shear modulus is zero.

What is the Bulk modulus for a perfect rigid body?

To what depth must a rubber ball be taken in deep sea so that its volume is decreased by 0.1%. (The bulk modulus of rubber is 9.8 × 10⁸ Nm^–2; and the density of sea water is 10³ kg m^–3.)