Therefore the work done by the string is zero when the pendulum bob swings from point II to pint III along the circular arc. Q.83     Define the term 'watt'.                 (d) conservation ; transformed ; created ; destroyed Solution: Chapter 7 Work And Kinetic Energy Q.89PP Microraptor gui: The Biplane Dinosaur The evolution of flight is a subject of intense interest in paleontology. If the player comes to rest at third base, (a) how much work was done on the player by friction? Line 2 is interesting in that it has the smallest slope that still touches the power-versus-speed curve. (ii) Maximum K.E at A. Q.108     A car of weight 20000 N climbs up a hill at a steady speed of 8 m/s, gaining a height of 120 m in 100 s. Calculate : Sol. Ex 6.2.4 A ladder 13 meters long rests on horizontal ground and leans against a vertical wall.                  (b) Cell (or Battery) Solution: Chapter 7 Work And Kinetic Energy Q.91IP Referring to Figure In the situation shown in Figure (d), a spring with a force constant of 750 N/m is compressed by 4.1 cm. Also of interest are the two dashed, straight lines labeled 1 and 2. The kinetic energy of this bullet in kJ will be :                (b) Watt-hour         (c) Kilowatt Sol. How much work does the force do on the block in moving it (a) from x = 0 to x = 0.30 m, or (b) from x = 0.10 m to x = 0.40 m?                 F = {{1200} \over {2 \times {{10}^{ - 2}}}} = 6 \times {10^4}N. (c) Determine the time required to accelerate from 5.0 m/s to 15 m/s.                K.E (of mass 2)  = {1 \over 2}m\,(6)^2 Sol.               (b) kilowatt-hour If your power output is 108 W, and the mass of the bucket and the water in it is 5.00 kg, with what speed can you raise the bucket? Give the SI unit of power. Solution: Chapter 7 Work And Kinetic Energy Q.60GP A Mountain bar has a mass of 0.045 kg and a calorie rating of 210 Cal. (c) How long does it take to lift the milk container through a distance of 1.0 m at this rate?               (b) The work done on a body moving in a circular path is ..........               (i) the amount of work done. Solution: From the figure it is clear that the approximate range of flight speeds would be possible if Microraptor gui could produce 20W of power is 2.5m/s to 25m/s. ben de bunlardan biriyim. (a) With what speed would the pinecone have landed if there had been no air resistance? Estimate the height a person could attain on a set of stairs using nothing more than the daily energy produced by the heart. A recently discovered fossil from the Cretaceous period in China supports the arboreal hypothesis and adds a new element—it suggests that feathers on both the wings and the lower legs and feet allowed this dinosaur, Microraptor gui, to glide much like a biplane, as shown in Figure. Solution: Chapter 7 Work And Kinetic Energy Q.8CQ A ski boat moves with constant velocity. Q.92     Name the device which converts electrical energy into mechanical energy. Sol. (a) How much work must be done by the brakes to bring the bike and rider to a stop? Consider a body raised to a certain height say h.If its velocity is zero, K.E will be zero. Measurements show that the active proteins within a muscle cell (such as myosin and actin) can produce a force of about 7.5 pN and displacements of 8.0 run.               (c) becomes 8 times that of initial kinetic energy (a)      What is the kinetic energy of ball when it hits the ground ? Estimate (a) the force and (b) the power produced by your jaw muscles during the bite.                    (ii) P.E \to K.E, Q.110     (a) State and explain the law of conservation of energy with an example. Unit of electricity. (b) Work done = Potential energy gained = 3920 J. Q.51     (a) Define the term 'work'. (i) When a body is in air and moving, it has both K.E and P.E. It seems to be certain then, that 2 joules are required to accelerate a 1 kg mass from zero to one meter per second in one second (ie accel=1m/s2) (a) 1kWh = 1000 W × 1h. It swings towards center position A and then to the other extreme position C. A freely falling body loses potential energy , but it gains equal amount of kinetic energy such that the sum total of energy remains constant. (b)      What is the potential energy of ball at B ? Because change in KE = K_f - K_i = 1200 J What speed would this candy bar have if its kinetic energy were equal to its metabolic energy? (i) Work done = F × d = (800 + 200) × 1200 = 12 × {10^5} J. Sol. Q.24      What are the quantities on which the amount of work done depends ? Sol. Solution: Chapter 7 Work And Kinetic Energy Q.40P Solution: Chapter 7 Work And Kinetic Energy Q.41P A block is acted on by a force that varies as (2.0 × 104 N/m)x for 0 ≤ x ≤ 0.21 m, and then remains constant at 4200 N for larger x. but the body will have                                                                             P.E = m × g × h. Work done = mgh Why, or why not? Number of steps = 28 = 1000 × 60 × 60 Doubling the velocity. Q.47     If the work done by a force in moving an object through a distance of 20 cm is 24.2 J, what is the magnitude of the force ? Chapter 7 Work And Kinetic Energy Q.43P Climbing the Empire State Building A new record for running the stairs of the Empire State Building was set on February 3, 2003. State the energy change which takes place : v = u + at = 0 + 10 × 2 = 20 m/s. Its K.E decreases and P.E increases. The bicycle moves through a certain distance. var h = now.getHours(); Chapter 7 Work And Kinetic Energy Q.19P How much work is needed for a 73-kg runner to accelerate from rest to 7.7 m/s? 1 Watt is the power of an object which does work at the rate of 1 Joule per second. (i) K.E = 0 at highest point because V = 0 Ladder Tree Stands Browse the complete lineup of Ladderstands at Lancaster Archery Supply, including Two Person Tree Stands with cushioned benches and padded shooting rails. Q.71     The work done by a force acting obliquely is given by the formula W = F \cos \theta x s. What will happen to the work done if angle between the direction of force and motion of the body is increased gradually ? (b) Various forms of energy are Light Energy , Chemical Energy , Nuclear Energy etc. Sol. (c) Initial K.E = {1 \over 2}m{v^2} = {1 \over 2} \times 0.5 \times {\left( {5} \right)^2} = 6.25 J.                 {\mkern 1mu} h = {1 \over 2}{{\left( {{v^2} - {u^2}} \right)} \over g} = {{ - 1} \over 2} \times {{{{20}^2}} \over {10}} = 10m. (ii) What is his potential energy at the highest point ? Joule. Calculate the power developed. Referring to Equation 7-13, we see that P/v = Fv/v = F, so the lines 1 and 2 correspond to lines of constant force.                 = 2.5 \times 10^{10} \times 5 \times 2 \times 60. Work done = 0    Work done is positive    Work done is negative, Q.30     A ball of mass 200 g falls from a height of 5 meters. As final velocity = 0. There are four major types of chemical reactions that break apart and build biological molecules.              (a) 6000 J        (b) 0.6 J          (C) 0       (d) 6 J                   (b) Zero (a) Power      (b) Energy. Solution: The force of friction always opposes relative motion, but if the body moves along the direction of applied force, for ◊ = 0º, the work done is positive. If the plane does 2.00 × 105 J of work to tow the glider 145 m and the tension in the tow rope is 2560 N, what is the angle between the tow rope and the horizontal? This is in the direction of force of gravity. Sol. Sol.              (e) A stretched spring lying on the ground. Q.73     In which of the following case the work done by a force will be maximum when the angle between the direction of force and direction of motion is 0° or 90°? Calculate the work done if the direction of force is at an angle of  60° to the horizontal surface. Andres Ruiz Sosa. Sol. (a) Calculate the resistive force exerted by the water on the kayak. document.write(''); Work done = m × g × h   , where g is acceleration due to gravity. Berks County. This curve shows how much power is required for flight at speeds between 0 and 30 m/s. If the force does not have non-zero components along the direction of motion, the work done is zero.                 (a) 0.3    (b) 1.2    (c) 3.0    (d) 6.0 When a body is raised, it has the capacity to do work i.e. Q.50     A weightlifter is lifting weights of mass 200 kg up to a height of 2 metres. ilk kapattığım günlerde sanki bir gözümü kaybetmişim gibi hissettim.                (a) increases                             (b) decreases The gravitational potential energy depends on Q.68     Which of the following does not possess the ability to do work not because of motion ? Sol. (b) How many Snickers candy bars (280 Cal per bar) would the pilot have to consume to be “fueled up” for the flight? Calculate its power rating. How much work is required to accelerate the car (a) from rest to the speed v0/2 and (b) from v0/2 to v0? (a) If the speed of the block in Figure (f) is 0.88 m/s, what is its mass? (b) What is the speed of the object at t = 2.0 s? (a) Joule (b) Joule. What type of work, positive or negative is done : No work is done by the gravitational force. Sol. This is know as elastic potential energy. This is opposite to the direction of force of gravity. Final K.E = {1 \over 2}m{v^2} = {1 \over 2} \times 0.5 \times {\left( 3 \right)^2} = 2.25 J. Solution: a) The pitcher does positive work on the ball because the direction of force is along the direction of displacement of the ball. Explain with an example. Q.125     A ball falls to the ground as shown below : (A)     Potential Energy = 80 J Also of interest are the two dashed, straight lines labeled 1 and 2. (iv) Chemical energy into heat energy. How long docs it take for the ice cube to melt? Thus, the change in kinetic energy = 0 joules ————- (1) Work done = change in kinetic energy —————- (2) From equations (1) and (2), work done = 0 joules ——————– (3) Work done = net force displacement ————— (4) Since the boat is moving at a constant speed, then from equations (3) and (4), net force = 0 newtons Thus, the net force is not doing any work on the boat. Sol. Q.69     A stone is thrown upwards . (b) What was the coefficient of kinetic friction between the player and the ground? This is because during the movement of the satellite, the force acting on it is always perpendicular to the direction of motion.              (b) A flying aeroplane Therefore option C. is correct.                  (b) Kinetic Energy (b) in 1 minute ? Q.74     How much work is done by the gravitational force of earth acting on a satellite.              (c) becomes 4 times that of initial potential energy Find the power delivered by gravity to the apple when the apple is (b) 2.5 m and (c) 1.5 m above the ground. Some subscribe to the “cursorial” (or ground-up) hypothesis, in which flight began with ground-dwelling animals running and jumping after prey. Work done = mgh ,where m is mass , g is acceleration due  to gravity and h is height. The increase in speed is the same in each case. Q.17     What is the kinetic energy of a body of mass 1 kg moving with a speed of 2 m/s ? (c) A horse and a dog are running with the same speed. Solution: Chapter 7 Work And Kinetic Energy Q.46P An ice cube is placed in a microwave oven.                (a) hydroelectric power stations use water to drive turbines Explain. Q.24      What are the quantities on which the amount of work done depends ? Solution: Chapter 7 Work And Kinetic Energy Q.81GP Solution: Chapter 7 Work And Kinetic Energy Q.82GP Powering a Pigeon A pigeon in flight experiences a force of air resistance given approximately by F = bv2, where v is the flight speed and b is a constant. Sol. Sol. (a) chemical energy to heat energy       (b) kinetic energy to heat energy Therefore the work done by the gravity is negative when the pendulum bob swings from point II to pint III along the circular arc. Sol. (b) By the piece of stone which is thrown away on releasing the stretched rubber strings of       catapult ? Solution: Chapter 7 Work And Kinetic Energy Q.72GP A juggling ball of mass m is thrown straight upward from an initial height h with an initial speed v0. Calculate the power. Sol.               (a) only potential energy                                   (b) only kinetic energy (b) Various forms of energy are Light Energy , Chemical Energy , Nuclear Energy etc. Electrical Energy \to Heat Energy \to Light Energy. Human-Powered Flight Human-powered aircraft re quire a pilot to pedal, as in a bicycle, and produce a sustained power output of about 0.30 hp. How much work do you do during this time?                   = 2.34 × {10^9}J, Q.113     (a) Define power. stove Solution: Chapter 7 Work And Kinetic Energy Q.59GP When you take a bite out of an apple, you do about 19 J of work.                 (b) someone speaks into a microphone                 = {1 \over 2} \times 150(10^2- 5^2 ) Work done = Change in K.E. Solution: Chapter 7 Work And Kinetic Energy Q.80GP A 1300-kg car delivers a constant 49 hp to the drive wheels. (ii) what is the potential energy of the package at A if it is assumed to be zero at B ? Q.28     How does the kinetic energy of a moving body depend on its (i) speed, and (ii) mass ? Con solucionario de problemas. (b) W = F × d What is its kinetic energy when it just reaches ground ? Explain. Q.107     The hanging bob of a simple pendulum is displaced to one extreme position B and then released. Solution: Chapter 7 Work And Kinetic Energy Q.38P To compress spring 1 by 0.20 m takes 150 J of work. The body pushing the truck does no work as displacement is zero. (c) Water stored in the reservoir of a dam. Sol. If the power output of the car remains constant, (a) how long does it take for the car to accelerate from v to 2v? Sc hu. Q.65     The momentum of a bullet of mass 20 g fired from a gun is 10 kg m/s. What quantity does it represent ? (Neglect air resistance friction) (C) Ladder, Extension. Sol. Solution: Frictional forces do negative work whenever they act in a direction that opposes the motion. (ii) Electrical Energy \to Heat Energy \to Light Energy. //var today = now.getFullYear()+"-"+(month)+"-"+(day); Give reason for your answer.              (d) becomes 16 times that of initial potential energy Q.75     A man is instructed to carry package from the base camp at B to summit A of a hill at a height of 1200 meters. (b) If the spring has the force constant found in part (a), find the maximum compression if the mass of the block is doubled and its initial speed is halved. This is the energy transferred by work done by hand .When we leave the bob, the bob moves down. Q.89     Name the quantity whose unit is : (b) Potential energy is the energy possessed by a body due to its position where as kinetic energy is the energy possessed by the body due to its motion. Choose all-steel Ladder Treestands for their solid construction and spacious seating. 3.6 \times {10^6}\,J. (b) If the speed of the car is doubled, does its acceleration increase, decrease, or stay the same? Sol. A freely falling body loses potential energy , but it gains equal amount of kinetic energy such that the sum total of energy remains constant. Q.122     The device which converts mechanical energy into energy which runs our microwave oven is : Q.37     A body of mass 100 kg is lifted up by 10 m. Find : (g = 9.8 m/{s^2})                \,Ratio\, = {{{1 \over 2}m(2)^2 } \over {{1 \over 2}m(6)^2 }} = {4 \over {36}} = {1 \over 9}, Q.33     A body of 2 kg falls from rest. When they are 10 m above the ground, they have the same : Work done = mgh ,where m is mass , g is acceleration due  to gravity and h is height. Carbon County. Solution: Chapter 7 Work And Kinetic Energy Q.83GP Solution: Chapter 7 Work And Kinetic Energy Q.84GP Solution: Chapter 7 Work And Kinetic Energy Q.85GP Solution: Chapter 7 Work And Kinetic Energy Q.86PP Microraptor gui: The Biplane Dinosaur The evolution of flight is a subject of intense interest in paleontology. Sol. Q.112     (a) Derive the relation between commercial unit of energy (KWh) and SI unit of energy (joule). (a) What is its kinetic energy in joules?               (a) 200 J        (b) 800 J    (c) 8000 J    (d) 2000 J Hence , the bob loses energy and eventually come to stop. Work done by brakes = Change in K.E. (b) Energy = P × t = 1000 × 1h = 1000 Wh = 1 KWh. Steps for Writing a Conclusion, Essay on Impact of Privatization | Impact of Privatization Essay for Students and Children in English, Essay on Child Trafficking | Child Trafficking Essay for Students and Children in English, Conversation Between Vegetable Seller and Customer | General, Funny and Dialogue Conversation Between Vegetable Seller and Customer, Global Warming Solutions Essay | Essay on Global Warming Solutions for Students and Children in English, Essay on TV Addiction | TV Addiction Essay for Students and Children in English, Essay on Dowry System | Dowry System Essay for Students and Children in English, Essay on Organ Trafficking | Organ Trafficking Essay for Students and Children in English. Solution: Chapter 7 Work And Kinetic Energy Q.92IP Referring to Example Suppose the car has a mass of 1400 kg and delivers 48 hp to the wheels. (a). Therefore the work done by the string is zero when the pendulum bob swings from point I to pint II along the circular arc. (b) At what rate must you lift a 3.6-kg container of milk (one gallon) if the power output of your arm is to be 22 W? Potential energy of water \to K.E of water \to K.E of turbines \to Electrical Energy. Sol. (b) How much work must you do to compress it 0.050 m? Solution: Chapter 7 Work And Kinetic Energy Q.44P How many joules of energy are in a kilowatt-hour? Explain your answer. Sol. Sol. (c) As K.E \propto \,m. (a) Work done is zero , since there is no displacement in the direction of force Use the following data to calculate the power of the student :                 (v) Solar water heater, Q.95     Fill in the following blanks with suitable words : if (i < 10) { Sol. Solution: Yes, we have to do work against the force of gravity to get out of bed in the morning because the constant force of gravity acts downward on our body when we are sleeping in bed. Sol. energy has been converted into kinetic energy so that it now has its maximum kinetic energy. Sol. (g = 9.8 m {s^{ - 2}}) Write the formula for the work done on a body when a force acts on the body in the direction of its displacement. Due to this it moves to the other side.                 = {{2500} \over {10 \times 5}} = 50\, Kg. The lower horizontal line shows the estimated 9.8-W power output of Microraptor, indicating the small range of speeds for which flight would be possible. Thermal energy is equal to the excess amount between food energy consumed (assume this to be 1.4 kcal = 5880 J) and work done. The final speed is twice the initial speed.                 (ii) Steam engine Sol.                (a) Watt                  (d) Kilowatt-hour What happens to its potential energy as its velocity becomes zero ? Sol. Sol. If it takes 201 J of work to do this, what is the combined mass of the dog and basket? Lehigh County.                 = 4.9 \times 10^4 J. (d) The push of a person's feet when standing on the floor Sol. Solution: 38ps Work done to compress spring 1 by x = 0.2 m is W = 150 J We know that. Solution: Chapter 7 Work And Kinetic Energy Q.48P In order to keep a leaking ship from sinking, it is necessary to pump 12.0 lb of water the second from below deck up a height of 2.00 m and over the side. (a) What is the acceleration of this car when its speed is 14 m/s? (c) What is the magnitude of the braking force? The work to accelerate the car depends on the speed squared. The truck does not move at all. The increase in speed from 50 km/h to 150 km/h is twice the increase in speed from 0 to 50 km/h. Sol. (i)At the position A (at height h above the ground): Initial velocity of body= 0 (since body is at rest at A) Hence, kinetic energy K =0 How much additional work is required to stretch it to 3 cm from equilibrium?                 \,Ratio\,\,of\,\,K.E\,is\,\,{{v^2 } \over {(2v)^2 }} = 1:4. er Riv. A simple pendulum with a bob of mass m swings with an angular amplitude of 40. One Watt is defined as the power when one Joule of work is done in 1 s. Q.84     How many Watts equal one horse power ? Q.101     How much electrical energy in joules does a 100 Watt lamp consume : var todaystime = h + ":" + m + ":" + s Another man Y of the same mass goes to the top of the same building by a slanting ladder.Which of the two does more work against gravity and why? If the value of g be 10 m/{s^2} , the work done by the girl against the gravitational force will be-:               (d) The principle of......of energy says that energy can be......from one form to another, but it cannot be......or...... (b) Calculate the change in speed in this case. The work done by the catapult during the launch is 7.6 × 107 J. (d) conservation ; transformed ; created ; destroyed.               (d) becomes 16 times that of initial kinetic energy (b) Did air resistance do positive work, negative work, or zero work on the pinecone? Sol. Sol.                (c) potential energy to sound energy    (d) chemical energy to kinetic energy Within the bus, the K.E does not depend on the speed of bus. Verify your answer with a calculation. Chapter 7 Work And Kinetic Energy Q.9CQ A package rests on the floor of an elevator that is rising with constant speed. Sol. If the sandy portion of the road had been only 16 m long, would the car’s speed have decreased by 3.5 m/s, more than 3.5 m/s, or less than 3.5 m/s? Always maintain 3 – point contact and avoid reaching beyond the side-rails of the ladder. His fist lashing out like a thunderbolt. Q.121     How much energy does a 100 W electric bulb transfer in 1 minute ? (c) Find an expression for the kinetic energy of the ball as it lands. Sol. Thus, the speed of the object will remain the same. (b) How much work do you do if you push the box for 35 s? Q.70     A boy tries to push a truck parked on the roadside.               (c) The electricity meter installed in our home measures electric energy in the units of...... Sol. Find the ratio of their kinetic energies.               (a) Mechanical energy into Electrical Energy. Q.119     An object is falling freely from a height x. Sol.                 Therefore, F × d = 1200. Solution: Chapter 7 Work And Kinetic Energy Q.9P A tow rope, parallel to the water, pulls a water skier directly behind the boat with constant velocity for a distance of 65 m before the skier falls. Q.72     What should be the angle between the direction of force and the direction of motion of a body so that the work done is zero ?. When it reaches P, which of the following has the greatest value for the stone ? (g = 10 m {s^{ - 2}}), Sol. No work is done when displacement is perpendicular to the direction of force. The lower horizontal line shows the estimated 9.8-W power output of Microraptor, indicating the small range of speeds for which flight would be possible. var today = day + "-" + month + "-" + now.getFullYear();                (c) sound energy into mechanical energy in a stereo system               (i) What is his kinetic energy at the highest point ? Solution: (a) When the pendulum bob swings from point II to point III along the circular arc, its displacement is upward.                = \left[ {\cos 60^\circ={1 \over 2}} \right]. SI unit of power is Watt . 80. As I have noted many times before, kinetic energy K of any particle with mass m is K=E-mc 2 where E is the total energy and mc 2 is the rest energy. (ii) maximum kinetic energy ? Change in K.E =  [{1 \over 2}m(v^2- u^2 )] (c) law of conservation of energy. Q.20      State whether the following statement is true or false The potential energy of a body of mass 1 kg kept at a height of 1 m is 1 J. Explain. When the water begins to fall, its potential energy is ... a person climbing a ladder a piece of celery blowing wind (b) A running car. (a) Is the work done on the bob by gravity positive, negative, or zero? ... Q.35 A man drops a 10 kg rock from the top of a 5 m ladder. (a) Kinetic energy -Law of conservation of energy states that energy can never be created or destroyed. Q.78     When a ball is thrown inside a moving bus, does its kinetic energy depend on the speed of the bus  Explain. What will be its potential energy at the end of 2 s? If the observation is taken from outside the train, its velocity will be different hence its K.E. 10 W. Q.88     How many joules are there in one kilowatt-hour ? Q.6     Is energy a vector quantity ? In one complete orbit, is the work done by the Earth on the space station positive, negative, or zero? Indicate ties where appropriate. The P.E decreases and K.E increases. i = "0" + i;                (d) Only potential energy Since kinetic energy = 1/2 mv^2, it follows that, for a given mass, a doubling of velocity requires a quadrupling of energy. Ratio of KE = = {{Mass{\mkern 1mu} of{\mkern 1mu} horse} \over {Mass{\mkern 1mu} of{\mkern 1mu} dog}}{\mkern 1mu} or{\mkern 1mu} {{Weight{\mkern 1mu} of{\mkern 1mu} horse} \over {Weight{\mkern 1mu} of{\mkern 1mu} dog}}  = {{10} \over 1} = 10. It can only change from one form to another. 3. il l ylk. Solution: Chapter 7 Work And Kinetic Energy Q.33P A 1.2-kg block is held against a spring of force constant 1.0 × 104 N/m, compressing it a distance of 0.15 m. How fast is the block moving after it is released and the spring pushes it away? (a) What is the kinetic energy of the object at t = 1.0 s? (a) Force ; distance How much work is done by such proteins? Q.46     How much is the mass of a man if he has to do 2500 joules of work in climbing a tree 5 m tall ? (a) Is the work required to accelerate the car from 50 km/h to 150 km/h equal to 2W0, 3W0, 8W0, or 91w0? (a) Work done by car = F × d =20,000 × 120 = 2400 KJ. Both the spheres are dropped simultaneously from a tower. As final velocity = 0. Is it correct to conclude that engine 1 does twice as much work as engine 2? 78. Sol. The kinetic energy is eventually converted to heat energy.