The K(alpha) X-ray of molybdenum has wavelength 71 pm. If the energy of a molybdenum atom with a K electron knocked out is 23.5 keV, what will be the approx energy (in keV) of an another molybdenum atom when an L electron is knocked out? 

A disc of radius 20 cm & mass 1kg is rolling with slipping on a flat horizontal surface. At a certain instant, the velocity of its center is 4 m/s and its angular velocity is 10 rad/s. The lowest contact point is O. Find angular momentum about any point on the ground at shown instant.

An airplane is in supersonic flight at an altitude h. At what smallest distance a (along the horizontal) from the observer on the ground is there a point from which the sound emitted by the airplane motors reaches to the observer earlier than sound emitted by plane when it is at point A that is directly above the observer. (υ_p = velocity of airplane, υ_s = velocity of sound.)

A potential difference is applied between a conducting sphere and a conducting plate (“plus” on the sphere and “minus” on the plate). The dimension of the plate are much larger than the distance between sphere and plate. A point positive charge is moved from point 1 to point 2 parallel to the plate. Using the above information choose the correct statement.

A long solenoid of cross-sectional radius R has a thin insulated copper wire ring tightly put on its winding. One half of the ring has the resistance 10 times that of the other half. The magnetic induction produced by the solenoid varies with time as B = bt, where b is a constant. Find the magnitude of the electric field strength in the ring.

A particle of mass 1kg is moving where potential energy varies with displacement U = 10 (1 – cos 2x), then  the time period of small oscillation about origin will be

Two blocks are connected by a string passing over a pulley as shown. Wedge is fixed. M is sliding down with speed 12 m/s at an instant and suddenly the string breaks. The coefficient of friction between the blocks and wedge is 1/√2. Find the velocity (in m/s) of block M with respect to m after t = 2 seconds from the moment the string breaks. [Take g = 10 ms^–2  and   Assume that the length of inclined is sufficiently long.]

In an experiment, a boy draws graph between V² (y-axis) and a² (x-axis) (where v =  velocity and a = tangential acceleration) for a simple pendulum. The graph is found to be a straight line of negative slope making an angle of 30° (with x-axis) when experiment was done on the ground and 60° (with x-axis) when experiment was done at height h above the ground. Then h must be (R = radius of earth)​​​ 

In the given circuit, initial charge on the capacitor is 1.5 C with polarity as shown in figure and current in the inductor is  zero. Now at t = 0 if the key k is closed, then the minimum current through the key is

A stationary sound source ‘S’ of frequency 334 Hz and a stationary observer ‘O’ are placed near a reflecting surface moving away from the source with velocity 2 m/sec shown in the figure. If the velocity of the sound waves in air is V = 332 m/sec, the apparent frequency of the echo is