If on an average 1 ship out of 10 do not arrive safely to parts . Find the mean and the standard deviation of the ships returining safely out of a total of 500 ships .

If on an average 1 ship out of 10 do not arrive safely to ports. Find the mean and the standard deviation of the ships returning safely out of a total of 500 ships.

If on an average 1 ship in every 10 sinks, find the chance that out of 5 ships atleast 4 will arrive safely.

Three ships A ,B ,a n dC sail from England to India. If the ratio of their arriving safely are 2:5, 3:7, and 6:11, respectively, then the probability of all the ships for arriving safely is a. 18/595 b. 6/17 c. 3/10 d. 2/7

A silver ball of radius 4.8 cm is suspended by a thread in a vacuum chamber, Ultraviolet light of wavelength 200nm is incident on the ball for some time during which a total light energy of 1.0 xx 10^-7 J falls on the surface. Assuming that on the average one photon out of every ten thousand is able to eject a photoelectron, find the electric potential at the surface of the ball assuming zero potential at infinity. What is the potential at the centre of the ball?

A box contains two 50 paise coins, five 25 paise coins and a certain fixed number N(geq2) of 10 and 5-paise coins. Five coins are taken out of the box at random. Find the probability that the total value of these 5 coins is less than 1 rupee and 50 paise.

A light rope fixed at one end of a wooden clamp on the ground passes over a tree branch and hangs on the other side. It makes an angle of 30^0 with the ground. A man weighing (60 kg) wants to climb up the rope. The wooden clamp can come out of the ground if an upward force greater than 360 N is applied it. Find the maximum acceleration in the upward direction with which the man can climb safely. Neglect friction at the tree branch. Take g=10 m/s^2

Figure shows water in a container having 2.0-mm thick walls made of a material of thermal conductivity 0.50Wm^(-1)C^(-1) . The container is kept in a melting-ice bath at 0^(@)C . The total surface area in contact with water is 0.05m^(2) . A wheel is clamped inside the water and is coupled to a block of mass M as shown in the figure. As the goes down, the wheel rotates. It is found that after some time a steady state is reached in which the block goes down with a constant speed of 10cms^(-1) and the temperature of the water remains constant at 1.0^(@)C .Find the mass M of the block. Assume that the heat flow out of the water only through the walls in contact. Take g=10ms^(-2) .

a. The top of the atmosphere is at about 400 kV with respectto the surface of the earth, corresponding to an electric field that decreases with altitude. Near the surface of the earth, the field is about 100 Vm^(-1). Why then do we not get a electric shock as we step out of our house into the openy (Assume the house to be a steel cage so there is no field inside!) b. A man fixes outside his house one evening a two metre high insulating slab carrying on its top a large aluminium sheet of area 1m^(2) . Will he get an electric shock if he touches the metal sheet next morning? c. The discharging current in the atmosphere due to the small conductivity of air is known to be 1800A on an average over the globe. Why then does the atmosphere not discharge itself completely in due course and become electrically neutral? In other words, what keeps the atmosphere charged? d. What are the forms of energy into which the electrical energy of the atmosphere is dissipated during a lightning? (Hint: The earth has an electric field of about 100 Vm^(-1) at its surface in the downward direction, corresponding to a surface charge density =-10^(-9) Cm^(-2) ?.

A spaceship is stationed on Mars. How much energy must be expended on the spaceship to launch it out of the solar system ? Mass of the space ship = 1000 kg, mass of the sun = 2 xx 10^(30) kg , mass of mars = 6.4 xx 10^(23) kg, radius of mars = 3395 Km: radius of the orbit of mars = 2.28 xx 10^(8) km , G = 6.67 xx 10^(-11) N m^(2) kg^(-2) .

A light rod of length 2m is suspended horizontally by means of 2 vertical wires of equal lengths tied to its ends. One of the wire is made of steel & is of cross section A_(1) = 0.1 cm^(2) & other of brass & is of cross section A_(2) = 0.2 cm^(2) , find out the position along the rod at which a weight must be suspended to produce (i) equal stresses in both wires, (ii) equal strains in both wires for steel, y = 20 xx 10^(10)Nm^(-2) & for brass y = 10 xx 10^(10) Nm^(-2) .