CBSE ADDA

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