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Class 7 Science Chapter 13 a .Tick The Class 7 Science Chapter 13 A .Tick the correct option 1.Which of the following device was not used earlier to measure time? Answer Quartz clock 2 the largest and sundialis located in Jaipur 3. the sundial for effective during bright day 4. Electronic watches use the vibration of crystals of quartz 5. Gane body covers equal distance in equal interval of time it to be said to be in uniform motion 6. Which of following does not show periodic motion Car moving at a constant speed 7. Motorcyclist moving on a busy cities road shows Non uniform and zigzag motion B. State whether the following statements are true or false 1. Sand clock is not an accurate device to measure the time True 2. Speed measure how slow or fast and object moves True 3 the basic unit of time is second True 4. A pendulum shows periodic motion True 5. Unknown uniform motion is presented by straight line on a distance time graph False 6.time period of pendulum does not depend upon the length of the string False C.Fill in the blanks 1. A pendulum works on the principle of periodic motion 2. Sand clock is also known as hour glass 3. Velocity of a moving body is distance travelled per unit time 4. A curveddistance time graph represent non- uniform motion 5.Amotion that repeats again and again is called periodic motion Non uniform motion 6. In modern wristwatches balance wheel has taken over the function of pendulum 7. 20 years = two decades D.Match the column Column A. Column B 1.Sun dial Jai Singh Ii 2.Quartz clock Crystal of quartz 3.unequal distances in equal intervals of time nonuniform motion 4.Equal distances in equal interval of time. Uniform motion 5.Pendulum clock periodic motion E.Give one word for the following 1. Comparison of unknown quantity with a known quantity of the same kind Measurement 2. Quantities that can be measured Physical quantities 3. The standard unit of mass Kilogram 4. The time taken by pendulum to complete one oscillation Time period 5. The instrument used in vehicles to indicate speed Speedometer 6. The instrument used to indicate distance covered by vehicle Odometer 7.the most accurate type of timepiece in the world designed to measure time according to vibrations within the atoms Atomic clock f.answer the following questions in brief 1 why are standard units used in measurements? Standard units are used in measurement because other units such as hand span are not appropriate because each person has different height. 2.Whch substance in electronic watches has taken over the function of vibration? Answer Fine crystals of quartz 3.What do you mean by 'time period' of a pendulum? Answer The time taken by the pendulum to complete one full oscillation is called a time period. 4.What is measurement? Answer The comparison of unknown quantity with a known toquantity of the same kind is known as measurement. 5.On what principle does a sundial work?What is drawback of a sundial? Answersundial works on the principle of shadow formation due to sunlight which varies is the position of sun in the sky. Drawback of this that it can be used during the day 6.Find the distance covered by a car traveling at the speed of 10m/s in 10 seconds. Answer Distance=Speed×time 10×10=100m 7.Convert a.Speed of 15m/s into Km/h Answer speed=15×18/5=54km/hr. b.Speed of 30km/hr into m/s Answer Speed=30×5/18=8.33m/s 8. Name two types of clocks used in ancient time. Answer Sundial and sand clock 9. Name two units of time other than SI unit Answer Hour and minutes G. Answer the following questions in detail 1.list out the different types of clothes used the early man explain each type Different types of clocks used in ancient time of sundial sand clock and water clock Sundial. Sundial works on the principle of shadow formation due to sunlight which varies with position of sun in the sky so it can be used during the daytime the length of shadow decrease is the time in the morning increasing in the evening few hundred year ago this clock was used Sand clock consist of two rounded glass bulbs above the other that are connected with the narrow glass tube and quantity of sand that trickles from the upper ball to the lower one this class cloak is also known as hour glass. Water clock water clock is a time ki pic device in which time is whether the regulated flow water into or out from The vessel where the amount of water measuredwater clock is a time keeping device in which time is measured by regulated flow water into or out from The vessel where the amount of water measured 2. Draw a diagram to a simple pendulum explain its working Answer. A pendulum consists of a metallic Bob with the hook thread is tied to the end of the thread is suspended to reduce pore when the pendulum is released from a distance it exists periodic motion single motion from a point of origin at the same point is oxidation with time taken by the pendulum to complete one oscillation is called time period 1 complete oxidation takes pleasure in box star from position A goes to position c and then compared to positionA 3Write a short note on a. Motion. When an object changes its position with respect to surrounding then the object is said to be in motion b. Uniform motion if a body travels equal distance in equal time interval that body said to be in state of uniform motion c. Non-uniform motion is a body travels an equal distance in equal interval of time the body is said to be known uniform motion d. A simple pendulum. Simple pendulum consists of metallic Bob with hook e. Speed the distance covered by body in a unit time is called speed 4. Explain the factor on which the time period of a simple pendulum depend time period of simple pendulum depends upon the length of the pendulum, acceleration due to gravity and the temperature (as length depends on temperature). It is directly proportional to the square root of length and inversely proportional to the square root of acceleration due to gravity 5.find the distance in metre travel by train in 20 minutes when travelling with a speed of 72 kilometre per hour Answer Speed=72km/h 72×5/18=20m/s Time=20minutes 20×60=1200s Distance=Speed×Time 20×1200=2400m .
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