Case-Study 2: Read the following passage and answer the questions given belowThree friends Ravi, Raju and Rohit were doing buying and selling of stationery items in a market. The price of per dozens of pens, notebooks and toys are Rupees x, y and z respectively. Ravi purchases 4 dozen of notebooks and sells 2 dozen of pens 5 dozen of toys. Raju purchases 2 dozen of toy and sells 3 dozen of pens and 1 dozen of notebooks. Rohit purchases one dozen of pens and sells 3 dozen of notebooks and one dozen of toys.In the process, Ravi, Raju and Rohit earn Rs. 1500, Rs. 100 and Rs. 400 respectively.
A man weight 60 kg climbs up a stair case with a 20 kg load on his head. The stair case has 20 steps and each step has a height 20 cm. The increase in potential energy of the man is (g=10ms−2)
A heater coil connected to 200 V has a resistance of 80 Ω. If the heater is plugged in for the time t such that 1 kg of water at 20°C attains a temperature of 60°C. Find the power of the heater.
Consider a planet in the solar system which has a mass double the mass of the Earth and a density equal to the average density of the Earth. For an object weighing W on the Earth, what will be the weight of the same object on the planet?
[22]The defective eye of a person has a near point 0.5 m and far point 3 m. The power for corrective lenses required for (i) reading purpose and (ii) seeing distant objects respectively are?
A concave lens has a focal length of 15 cm. At which distance should the object from the lens be placed so that it forms an image at 10 cm from the lens? Also, find the magnification of the lens.
A convex lens has a focal length of 10 cm. At what distance from the lens should the object be placed so that it forms a real and inverted image 20 cm away from the lens?
A diverging lens has focal length 20 cm. An object of height 4 cm is placed 20 cm from the optical centre, in front of the lens. The image is formed at 10 cm away from it. The size of the image formed is
The size of the image of an object by a mirror having a focal length of 20 cm is observed to be reduced to 1/3 rd to its size. At what distance, the object has been placed from the mirror?
