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

Will ultrasonic waves show any polarization? Give reasons for your answer.

If one of the angles formed by two intersecting lines is a right angle, what can you say about the other three angles? Give reasonf for your answer.

Earth rotates about its axis in _______ direction.

Torques of equal magnitude are applied to a hollow cylinder and a solid sphere, both having the same mass and radius. Hie cylinder is free to rotate about its standard axis of symmetry, and the sphere is free to rotate about an axis passing through its centre. Which of the two will acquire a greater angular speed after a given time.

A bullet of mass 10 g and speed 500 m//s is fired into a door and gets embedded exactly at the centre of the door. The door is 1.0 m wide and weighs 12 kg. It is hinged at one end and rotates about a vertical axis practically without friction. Find the angular speed of the door just after the bullet embeds into it.

In the figure. The straight wire AB is fixed, while the loop is free to move under the influence of the electric currents flowing in them. In which direction doe the loop begin to move? Give reason for your answer.

A closed tube, partly filled with a liqyid and set horizontal, is rotated about a vertical axis passing through its centre. IN the process, the moment of inertia of the system about its axis would

A compass needle free to turn in a horizontal plane is placed at the centre of a circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of 45^@ with the magnetic meridian when the current in the coil is 0.35amp., the needle points west to east. The current in the coil is reversed and the coil is rotated about its vertical axis by an angle of 90^@ in the anticlockwise sense looking from above. Predict the direction of the needle. Take the magnetic declination at the places to be zero.

A compass needle free to turn in a horizontal plane is placed at the centre of circular coil of 30 turns and radius 12 cm. The coil is in a vertical plane making an angle of 45^@ with the magnetic meridian. When the current in the coil is 0.35 A, the needle points west to east. The current in the coil is reversed, and the coil is rotated about its vertical axis by an angle of 90^@ in the anticlockwise sense looking from above. Predict the direction of the needle. Take the magnetic declination at the places to be zero.