Words of length 10 are formed using the letters, A, B, C, D, E, F, G, H, I, J. Let x be the number of such words where no letter is repeated ; and let y be the number of such words where exactly one letter is repeated twice and no other letter is repeated. Then, y/9x=?

Devendra Yadav Maths 10 Dec, 2017 1 Answer 2048 views

A stationary source emits sound of frequency f0 = 492 Hz. The sound is reflected by a large car approaching the source with a speed of 2 m/s . The reflected signal is received by the soruce and superposed with the original. What will be the beat frequency of the resulting signal in Hz? (Given that the speed of sound in air is 330 m/s and the car reflects the sound at the frequency it has received).

Devendra Yadav Physics 10 Dec, 2017 1 Answer 759 views






























When a current of 5 mA is passed through a galvanometer having a coil of resistance 15Ω, it shows full scale deflection. The value of the resistance to be put in series with the galvanometer to convert it into a voltmeter of range 0 – 10V is?

Preeti Rai Physics 09 Dec, 2017 1 Answer 2287 views



For three events A, B and C, P(Exactly one of A or B occurs) = P(Exactly one of B or C occurs) = P (Exactly one of C or A occurs) = 1/ 4 and P(All the three events occur simultaneously) = 1 /16 . Then the probability that at least one of the events occurs, is?

Devendra Yadav Maths 08 Dec, 2017 0 Answer 65 views




The most abundant elements by mass in the body of a healthy human adult are: Oxygen (61.4%); Carbon (22.9%), Hydrogen (10.0%); and Nitrogen (2.6%). The weight which a 75 kg person would gain if all H atoms are replaced by 2H atoms is?

Devendra Yadav Physics 08 Dec, 2017 1 Answer 2246 views

A capacitance of 2 µF is required in an electrical circuit across a potential difference of 1.0 kV. A large number of 1 µF capacitors are available which can withstand a potential difference of not more than 300 V. The minimum number of capacitors required to achieve this is?

Devendra Yadav Physics 08 Dec, 2017 1 Answer 316 views


In a Young’s double slit experiment, slits are separated by 0.5 mm, and the screen is placed 150 cm away. A beam of light consisting of two wavelengths, 650 nm and 520 nm, is used to obtain interference fringes on the screen. The least distance from the common central maximum to the point where the bright fringes due to both the wavelengths coincide is

Preeti Rai Physics 08 Dec, 2017 1 Answer 670 views

A copper ball of mass 100 gm is at a temperature T. It is dropped in a copper calorimeter of mass 100 gm, filled with 170 gm of water at room temperature. Subsequently, the temperature of the system is found to be 75 C. T is given by: (Given : room temperature = 30 C, specific heat of copper = 0.1 cal/gm C)

Preeti Rai Physics 08 Dec, 2017 1 Answer 213 views


For three events A, B and C, P(Exactly one of A or B occurs) = P(Exactly one of B or C occurs) = P (Exactly one of C or A occurs) = 1 /4 and P(All the three events occur simultaneously) = 1/ 16 . Then the probability that at least one of the events occurs, is:

Devendra Yadav Maths 07 Dec, 2017 1 Answer 1299 views

Two reactions R1 and R2 have identical pre exponential factors. Activation energy of R1 exceeds that of R2 by 10kj /mol. if k1 and k2 are rate constants R1 and R2 respectively at 300 K, then In (K2/K1) is equal to? Given (R=8.314 J/mol K)

Preeti Rai Chemistry 07 Dec, 2017 2 Answer 660 views


The fallowing observations were taken for determine surface tension T of water by capillary method: diameter of capillary, D = 1.25 * 10^-2 m rise of water, h = 1.45* 10^-2m Using g = 9.80 m/s^2 and the simplified relation T = rhg/2*10^3 N/m, the possible error in surface tension is closest to?

Devendra Yadav Physics 07 Dec, 2017 1 Answer 388 views


A car is standing 200 m behind a truck which is also at rest.The two start moving at the same instant but the different forward accelerations.The truck has acceleration 2 m/s^2 and the car has acceleration 4m/s^2. The car will catch up with bus after a time?

Rahul Kumar Physics 12 Sep, 2017 1 Answer 1658 views