Floatation+Sound+Work and Energy
1. Seema purchased a new pair of high heeled fashionable shoes. During a picnic organized by her school Seema intentionally wore these high heeled shoes for showing off to her classmates. However, Seema could not walk as comfortably as her classmates during the picnic. After walking through some distance she felt tired. Her friend Hema held her hand firmly and helped her in walking. Later on, Hema advised Seema to wear shoes of flat sole on such a trip. Seema
Bought flat shoes and now she felt more comfortable while walking.
a) Why Seema could not walk properly and comfortably during her school picnic?
b) A girl weighing 400N wear high heel shoes. If she stands on one foot only and the area of heel be 5cm2, what pressure is acting on the heel?
c) What value was shown by Hema?
2. Raman lived in a village situated in a hilly area. There was a beautiful lake near the village. During vacations Raman usually went to visit around the lake. Sometimes he used to sit just near the bank of lake with his legs immersed in lake water. Raman observed that it is easier to raise or move his legs inside water than in air. He could not understand the cause of it. He asked his elder brother Mohan. Mohan told him that it is due to force of buoyancy in accordance with Archimede’s principle. Mohan explained the principle in detail to Raman. Now Raman was happy as he knew the exact explanation of his observation.
a) In your opinion what is buoyant force? Under which condition does it act?
b) State Archimede’s principle.
c) What quality was shown by Raman? What quality was shown by Mohan?
3. Once Sanya and her brother Satvik went to Chandigarh to spend their holidays with their uncle’s family. One day Sanya, Satvik and their cousins visited Sukhna lake. They found that motor boats are available. They decided to have a boat ride in Sukhna lake. They were provided special jackets and were asked to wear the jackets before going on to the boat. Young Satvik could not understand the purpose of wearing the special jacket over and above his normal clothing. Sanya’s cousin brother Abhishek, who was a student of class X, knew the function of jacket. He said that the jacket is a life saving jacket and explained its working principle. Now Satvik was assured of his safety and wore the jacket. They had a happily boat riding in Sukhna lake for one hour.
a) What is the fuction of air filled life saving jacket and how does it work?
b) What were the doubts of Satvik? How did Abhishek clear these doubts?
c) State the law of Floatation.
4. Sita and Radha were close friends and both were students of 8th standard in same school. Sita felt burdened while carrying her school bag in her hand or on her shoulders. She also observed that it was easier to carry Radha’s school bag, although it was as heavy as it was her own. He could not know the reason for this anomly and daily felt pain in her shoulders while carrying her school bag. Radha told her the difference. While strap of Radha’s school bag was broad and thick, the strap of Sita’s bag was made of thin and strong string. Radha presented a new schoolbag having a broad and thick strap to Sita. When Sita used that bag she did not feel any burden in carrying her school bag. Now she was happy and satisfied.
a)Why is it difficult to hold a school bag having a strap made of a thin and strong string?
b) Define pressure and give its SI unit.
c) What value was shown by Radha?
(WORK AND ENERGY)
1. An old man was waiting for a roadways bus at a bus stand with his heavy luggage bag in his hands, He was tiring and used to shift the bag from one hand to another and so on. Shashank was seeing this. He felt uneasy and requested the old man to put his bag on the floor of bus stand near him so that he may be free. Initially the old man looked suspiciously towards Shashank but on persuation he agreed and put his heavy bag on the floor and carefully set on it. Now he was relieved and peaceful.
a) Was the old man applying some force while holding the bag in his hand? If yes, of what type?
b) Was the old man doing some work while holding the bag in his hand? Why?
c) What value was shown by Shashank?
2. On a Sunday evening Anamika was preparing a chart for a science project in her room. Her mother asked Anamika to help her in kitchen but Anamika said that she was too busy and doing a very important work. By the time Anamika completed her chart, she felt tired and hungry. She took her dinner and went to bed.
a) Was Anamika actually doing work from physics point of view? Give reason.
b) What type of work was Anamika doing?
c) Why did she felt tired and hungry?
d) What quality was displayed by Anamika?
3. There was a bad habit in Gopal’s family. Nobody used to switch off electric bulbs/tubes/fans etc., even when not being required. Due to this they have to pay a huge amount as the electricity bill per month. Gopal’s physics teacher explained in the class the importance of energy savings. He gave an example that a CFL lamp of 18W rated power almost gives same light as a 100W incandescent bulb but saves energy. Gopal requested all his family members about energy savings. They used to switch in electrical appliances only when needed. They also replaced bulbs with CFLs. Next month the amount of electricity bill of their house was quite less than it used to be earlier. Now they all acknowledged the importance of energy saving.
a) What is power? What is its SI unit?
b) In which unit the electric energy consumed is measured? What is its value in joules?
c) What should we try to save consumption of energy?
d) What value was shown by Gopal? What was the result of his efforts?
4. Rajni was swinging on a swing in her society park. She wanted to increase the speed of the swing. She started pushing the ground backward harder with her feet, when her swing was at its lowest position during its oscillations. She enjoyed it but did not show the actual mechanism. Her elder brother Ajay told her the actual mechanism of gaining speed in a swing.
a) What type of energy was possessed by Rajni while swinging on a swing? On what factors does it depend?
b) Why did the swing speed increased when Rajni pushed back the ground harder?
c) What conclusion do you draw about the characteristic quality of Rajni from the above?
VALUE BASED QUESTIONS (SOUND)
1. Rajesh went to a hill station with his parents and elder sister Shashi. He was experiencing the scenic beauty of a hill station for the first time. One day they were walking in a forest area, Rajesh loudly called”Shashi, Shashi didi “and so on. To his surprise he could distinctly hear the same sound twice. He thought that somebody is present in the forest area who is mimicking his voice. He started weeping. Hearing her weeping sound Shashi came near him, consoled him and explained the true cause of repetition of sound and told him that the phenomenon is called echo. Rajesh was satisfied now. When they returned to their hotel room, Rajesh shouted loudly in the hotel room but now there was no echo.
a) What is echo? How is it formed?
b) Why did not Rajesh hear any echo in his hotel room?
c) What value was shown by Shashi, the sister of Rajesh?
d) A person speaks in front of a huge building and hears an echo exactly 2 s afterwards. What is the distance of the building from the person? Speed of sound=340m/s.
2. Ravi and Vikas were feeling bored during a vacation. Vikas had an idea. He asked Ravi to prepare a toy telephone set. They took two small size plastic glasses and a long thread. Using a needle, they drilled small holes in two glasses and tied the ends of thread to two glasses by passing the thread through the holes. Now they stood apart with one plastic glass with Ravi and the other with Vikas. Ravi spoke softly in to his plastic glass and vikas was able to clearly listen the sound. Then Vikas answered softly in his plastic glass and Ravi could listen the message. Now both of them were happy. They showed their telephone set to their friends too.
a) How the sound was travelling from one end of thread to another? Explain the mechanism.
b) How is sound produced? Can sound travel through vacuum?
c) What quality was exhibited by Vikas and Ravi?
3. Swati lived in her apartment situated on the 4th floor of a multistory building in Gurgaon. One day she observed from the window of her room that a bansuri made of bamboo reed. She started playing with it. She found that if one blows gently at the mouth of Bansuri, the sound produced was soft but when blown with more power, the sound produced was a loud sound. Using her fingers she closed all the holes of Bansuri and blew at its mouth and found the sound to be a low pitched sound. However, when she opened different holes by removing fingers from the holes. She found the sound to be a sharp, high pitched sound. She asked her father, why it is so. Her father explained the detailed mechanism of production of sound waves in air to her.
a) What type of waves is produced in the air column of Bansuri?
b) What is the difference between a soft sound and a loud sound?
c) What is the difference between a low pitched sound and a high pitched sound?
d) What quality was shown by Swati?
4. Narender studies in class VII. Once he was suffering with cold and cough and was running high temperature. His mother took him to a doctor. The doctor examined the chest and back of Narender with the help of a device ‘stethoscope’. While examining with stethoscope doctor asked Narender to take longer breathings. After examining Narender the doctor prescribed some drugs. By regular use of these drugs Narender was normal within four days. But he could not understand the purpose of being examined by the use of stethoscope. During winter break his cousin Mukesh, who was studying in a medical college, visited their place. On the request of Narender, Mukesh explained to him the exact purpose of stethoscope and its action.
a) What is stethoscope? What is its use?
b) How does a stethoscope work?
c) Name two other devices which work on the principle as being utilized in a stethoscope?
d) What quality was shown by Narender and what by Mukesh?
Thanks to : Source:davpushpanjali
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I am a school teacher and serving CBSE students community since 1995.