Q.1. Can kinetic energy of a body be negative?
No as m ass and velocity cannot ne negative Q.2. A freely falling object eventually stops on reaching the ground. What happens to its kinetic energy? A freely falling object just before hitting the ground has maximum kinetic energy. After falling, it rolls on the rough ground and finally comes to rest. The kinetic energy of the object is used up in doing work against friction; which finally appears as heat energy. Q.3. Find the energy in kWh consumed in 10 hours by four devices of power 500 W each. Energy consumed = Power x time taken = 2000W x 10 h = 20000 Wh = 20 kWh. Q.4. Calculate the work required to be done to stop a car of 1500 kg moving at a velocity of 60 km/h? The work required to be done to stop a car = ( ½ mu2) - ( ½ mv2)= ½ m(u2-v2)= 1/2x1500(602-0)=2.08J Q.5 What is the work done by the force of gravity on a satellite moving round the Earth? Justify your answer. The work done by the force of gravity on a satellite moving around the Earth is zero. When a satellite moves around the Earth in a circular path, then the force of gravity acts on it directed towards the centre. The motion of the satellite is in the horizontal plane. Therefore, the force of gravity of Earth on the satellite and the direction of motion of satellite are perpendicular to each other. Therefore, net work done = Fs cos 90 = 0. Q.6. The potential energy of a freely falling object decreases progressively. Does this violate the law of conservation of energy? Why? During the free fall of the object, there is continuous decrease in potential energy. This decrease in potential energy appears as an equal amount of increase in kinetic energy. Thus, the sum of the potential energy and kinetic energy of the object would be the same at all points. That is, potential energy + kinetic energy = constant. According to the law of conservation of energy, the total energy of system remains unchanged. Thus, the given statement does not violate the law of conservation of energy. Define 1 J of work. Work done = Force x Displacement If force, F = 1 N and displacement, s = 1, m then the work done by the force will be 1 Nm or1 J. Thus, 1 J is the amount of work done on an object when a force of 1 N displaces it by 1 m along the line of action of the force. Download other study material on Work, Energy And Power
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1. Describe at least three rules of measuring length correctly.
Ans: a. The scale that you are using to measure the object must be greater than the length of the object. b. The eye should be placed just above the points that you are reading otherwise there will be error due to parallax. c. If the zero mark of the scale is damaged or edge of scale is not smooth, then start measuring from another mark. 2. Name two devices used to measure length. Ans: The two devices that can be used to measure length are:- Metre scale ad Screw gauge. 3. Describe the correct method of measurement of length. Ans: (i) we must choose a suitable device for measuring the length of an object, like measuring scale (ii) we should place the scale in contact with an object along its length and align the zero mark of the scale with the starting position of the object. (iii) While taking the reading, eye must be placed vertically above the point where the measurements have to be taken; otherwise there will be an error in the reading which is taken due to parallex. (iv) if the zero mark on the scale is damaged, then start the measurement from another mark. 4. Circle odd one (a)Table; fan; falling stone; Parked car (b)Bee ; butterfly; Grazing Cow; Sleepy Donkey (c)Pendulum; Earth revolving around the Sun; Moon revolving around the earth; Bee revolving on flowers (d)Moving fan; merry go round; A bus moving on road; a stone moving along circular track Ans: (a) falling stone (b) Sleepy Donkey (c) Bee revolving on flowers (d) A bus moving on road 5.Fill in the blanks 1.One meter is --------------cm 2.one centimeter is -----------------mm 3. Four km is ---------m 4. The motion of moving bicycle is ---------------- 5. The motion of drill machine is ---------- 6. Motion of child on swing ------------- 7. The motion of a top is ---------- Ans: 1. 100 2. 10 3. 4000 4. Rectilinear 5. rotatory 6. oscillatory 7. rotatory 6. Say true or false (a)Rectilinear and curvilinear cannot happen at the same time (b)Rupa can move in rectilinear and rotationary motion at the same time (c)A child on swing has only circular motion (d) Periodic motion is always rectilinear (e) A foot step is used as a standard unit of length. Ans: (a)False (b)True (c) False (d) False (e)False Hots questions: 1. Can an object be in motion and rest simultaneously for different observer? Give an example and consequence? Ans: Yes. A person driving a car is in rest with respect to other person in car but in motion with respect to a person standing road side. Tate of motion and rest depend on the observer or a fix point called reference point. 2. Can a body be in translational and rotational motion? Give some examples Ans: yes, combination of translation and rotation is rolling motion like the motion of the wheel , the motion of the earth, drilling. 3. Why do we need standard unit of measurements for a quantity? Ans: The unit used like hand span ,foot, cubit differ from person to person or even in different countries so for a uniform measurement we need standard unit of measurements. 4. Is it correct to say all periodic motion are oscillatory motion and all oscillatory motion are periodic. Give reason for answer? Ans: In oscillatory motion body repeat its action in equal interval of time so, all periodic motion are oscillatory motion and vice versa. For example motion of swing, pendulum, motion of earth on its axis. Post related to this chapter: Short Questions and Solution : Motion and Measurement of Distances Long Questions and Solution : Motion and Measurement of Distances VI 6th Science Assignments:: CH-6 Measurement and Motion Points to Remember :
1. Tangent to a circle at a point is perpendicular to the radius through the point of contact. 2. From a point P, lying on the circle, one and only one tangent can be drawn to it. 3. From a point, lying outside a circle, two and only two tangents can be drawn to it. 4. The lengths of the two tangents drawn from an external point to a circle are equal. 5. If two circles touch internally or externally, the point of contact lies on the straight line through the two centers. NCERT Solution X Ch-10 - Circles by topper learning View/Download File 10th Chapter : Tangent of Circle CBSE Test Paper-1 10th Chapter : Tangent of Circle CBSE Test Paper-2 10th Chapter : Tangent of Circle CBSE Test Paper-3 10th Chapter : Tangent of Circle CBSE Test Paper-4 10th Ch:Tangent of Circle CBSE Test Paper Solved -1 View/Download File Physics: IX Work, Energy and Power Study notes and CBSE Guess and Test Paper also download Numerical
Work : Product of magnitude of force and the magnitude of displacement of the body during time in which force acts is called work. Work is a scalar quantity. If W, F and s indicate work, force and displacement respectively then the work is given by the following formula. W = F s SI unit of work is newton metre (Nm) which is also known as joule in memory of famous physicist Joule. Thus, for work to be done, action of force is necessary as well as displacement in the direction of force is also necessary. What will be the work done if angle between the force and displacement is 900 ? Ans: work done is zero View full Paper Physics: IX Work, Energy and Power Also you may like WORK POWER ENERGY QUESTIONS & ANSWERS FOR CLASS XI CBSE View 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/s2
Ans: Pressure is given as force/area so, Force, F = mg = 1000 X 981 gm.m/s2and area, A = 1x1 cm2 = 1 cm2Thus, the pressure exerted would be P = (981 X 1000) / 1 or P = 9.81 X 10 5 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/cm3, 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/cm3Mass= 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 relative density. (Density of water at 4 degree C is 10 cube kg minus cube) Ans:Relative Density = Density of Substance/ Density of water at 4 0cDensity of turpentine oil = 840 kg/ m3 ( given).Density of water at 4 0c = 1000 kg/ m3Relative density of turpentine oil = Density of turpentine oil / Density of water at 4 0c= (840 / 1000 ) kg m-3/ kg m-3 = 0.84Since, the relative density of the turpentine oil is less than 1, therefore it will float in water. Q. A solid body of mass 150 g and volume 250cm3 is put in water . will following substance float or sink if the density of water is 1 gm-3? Ans: Visit link for full question solved for 9th CBSE board |
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