CBSE ADDA

Q. a cube of mass 1kg with each side of 1cm is lying on the table. find the pressure exerted by the block on the table. take g=10 m/s 2 Ans: Pressure is given as force/area  so, Force, F = mg = 1000 X 1000 gm.cm/s 2 and   area, A = 1x1 cm 2  = 1 cm 2 T hus, the pressure exerted would be P = (1000 X 1000) / 1 or P = 1 x 10  6  pa Q. The mass of a solid iron cube of side 3cm is to be determined usig a spring balance. If the of iron is approximately 8.5 g/cm 3 , the best suited spring balance for determining weight of the solid would be of  1. range 0-250gwt ; least count 1gwt              2. range 0-250gwt ; least count 5gwt 3. range 0-1000gwt ; least count 5gwt            4.  range 0-1000gwt ; least count 10gwt Ans: Edge=3 cm ,  Density=8.5 g/cm 3 Mass=  density x volume = 8.5 x(3x3)=229.5gwt Therefore second spring balance of range 0-250 gwt with least count 5gwt will be suitable. Q. The density of turpentine oil is 840 Kg/ m3. What will be its relati

CBSE PHYSICS: CBSE Work, Energy and Power IX Physics assignment 1. Under what conditions work is said to be done? 2. Derive the formula for work done by a constant force 3. Give few examples where energy is possessed by a body due to its change in shape. 4. State and prove the law of conservation of energy. 5. Is it possible that force is acting on a body but still work done is zero? Explain. 6. A rocket of mass 3x106 kg takes off from a launching pad and acquires a vertical velocity of 1km/s at an altitude of 25 km. calculate (a) the potential energy and (b) the kinetic energy. (g = 9.8m/s 2 ) 7. If a man lifts a load up with the help of a rope such that it raises the load of mass 50kg to a height of 20m in 100 sec. Find the power of man 8. A ball is dropped from a height of 5m. Find the velocity of the ball just before it reaches the ground. Do you require the value of mass to find the velocity? 9. Two persons A and B do same amount of work. The person A does

Question:  A person has a hearing range from 20 Hz to 20 kHz. What are the typical wavelengths of sound waves in air corresponding to these two frequencies? Take the speed of sound in air as 344 ms–1 .  Ans. (I) Wavelength of sound waves corresponding to 20 Hz, u = u = 344 ms–1, v = 20 Hz λ 1  =  v/n = 334/20  = 17.2 m  λ 2 =v/n = 334/20,000  = 0.0172 m Question:   The frequency of a source of sound is 100 Hz. How many times does it vibrate in a minute? Ans. Frequency of sound = 100 Hz = 100s –1   Number of vibrations in 1 s = 100 Number of vibrations in 1 minute, i.e. 60 seconds =100x60 =6000vibrations Question:   Explain how bats use ultrasound to reach a prey. Ans. Bats produce high pitched ultrasonic waves that are not heard by humans. These ultrasonic waves strike the prey like an insect and it is reflected back in the form of an echo, which is heard by the bat. This enables the bat to hover on the insect and catch it. Question:   A sonar device on a subma

CBSE PHYSICS: ASSIGNMENT FOR THE SESSION 2011-2012 Class: IX Sub... JSUNIL TUTORIAL: Section A : Physics Q.1. Define work energy and power. Give the proper SI units. Hence derive the expression for kinetic and potential energy. Q.2. State and prove the principle of conservation of energy. Also prove work energy theorem. Q.3. A boy is moving on a road against a frictional force of 5N. After travelling a distance of 1.5km,he forgot the correct path at a roundabout (figure) of radius 100m. However he moves on a circular path for one and half cycle and then he moves forward upto 2 km. Calculate the workdone by him. Q.4. Weight of a wooden piece is 6 kg.While floating in water its 1/3 rd volume remains submerged in water. Calculate the maximum weight that may be placed on it so that it may float completely submerged. Q.5. When a boat floats in water its one fourth volume remains submerged. The maximum weight that can be placed on boat is 1200 kgf. Calculate the weight of empty boat. Q.6. Ex

Class 6th Area and Perimeter -1 1. Find perimeter of rectangle whose length =6m8dm and breadth = 4m 6dm 2. Find the cost of fencing rectangle field 24n long and 18m wide at Rs. 6.25 per meter. 3. The length and breadth of rectangle field are in ratio 5:3. If its perimeter is 64m. Find the dimensions. 4. The cost of fencing a rectangle field at Rs. 14.60 per m is 1606. If the width of the field is 23m find its length. 5. The length and breadth of rectangle field are in ratio 3:2. The cost of fencing the field at Rs. 6.50 per m is Rs. 520. Find the dimensions of the field. 6. The cost of putting fence around a square field at Rs. 15 per m is Rs. 432. Find the length of each side of the field. 7. Each side of square is of 21m. Adjacent to this field, there is a rectangular field having its side in ratio 4:3. If perimeters of both fields are equal find the dimensions of the rectangular field. 8.Find the circumference of circle if r =14cm 9. Find the diameter of circle if circumference

CBSE MATH STUDY: Assignment CBSE IX Mathematics Surface area and... : 1.The diameter of garden cylindrical roller is 2.8m long . How much area will it cover in 100 revolutions. 2. A rectangular piece of paper 16 cm by 3.5cm is rotated about the longer side. Find the total surface area of the solid so generated. 3. In a hot water heating system, there is a cylindrical pipe of length 35m and radius 4cm find the total radiating surface in the system 4. Find the curved surface area of the right circular cone whose slant height is 10cm and base radius is 7cm. IX Mathematics Surface area and... :

1. Relative density of silver is 10.8. The density of water is 10 3   Kgm -3 . What is the density of silver in SI unit?  Ans: Relative density of silver = 10.8 Relative density of water = 10 3   Kgm -3 Density of silver = Relative density of silver x Relative density of water = 10.8 x 10 3   Kgm -3 2. Is potential energy a vector or a scalar quantity? Ans: Potential energy is a scalar quantity. 3. (i) Give any two examples of longitudinal waves.(ii) What is the most essential property of a wave motion and why? Ans: (a) i. Waves produced in air. ii. When a freely suspended spring is pulled downwards and released, longitudinal waves are produced. (b) The most essential property of a wave motion is its frequency. Frequency of a wave is its inherent characteristic and does not change by the change in temperature, pressure or change in medium. 4. (a) Calculate the work done in lifting 200 kg of water through a vertical height 6 meter. (Assuming g = 10m