(b) kilowatt-hour Chapter 7 Work And Kinetic Energy Q.3P A pendulum bob swings from point II to point III along the circular arc indicated in Figure. How does the kinetic energy of the sled and birds compare with the initial kinetic energy of the sled before the birds landed? stove What type of work, positive or negative is done : Chapter 7 Work And Kinetic Energy Q.26P At t = 1.0 s, a 0.40-kg object is falling with a speed of 6.0 m/s. The kinetic energy is eventually converted to heat energy. (ii) maximum kinetic energy ? What will be its kinetic energy during the fall at the end 2 s ? Therefore, F × d = 1200. Always maintain 3-point contact and avoid reaching beyond the side-rails of the ladder. A minimum of 8.1 W is needed for flight at 10 m/s. = 650 × 3.6 × {10^6}J 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. You lift the 3.2-kg pumpkin to a height of 1.2 in, then carry it 50.0 m (on level ground) to the check-out stand. K.E \propto \,v^2. (e) Only potential energy (rather elastic potential energy). (d) sound energy into electrical energy in public address system Sol. Lehigh County. Sol. (b) Energy = P × t = 1000 × 1h = 1000 Wh = 1 KWh. Explain. (b) Suppose the spring is already stretched 2 cm from equilibrium. So when man walks on the ground, the frictional force between his shoes and the ground does positive work whenever he begins to walk, as ◊ = 0º. Sol. Solution: Chapter 7 Work And Kinetic Energy Q.66GP A work W0 is required to stretch a certain spring 2 cm from its equilibrium position. Solution: Chapter 7 Work And Kinetic Energy Q.42P CE Force F1 does 5 J of work in 10 seconds, force F2 does 3 J of work in 5 seconds, force F3 does 6 J of work in 18 seconds, and force F4 does 25 J of work in 125 seconds. (i) in the battery. (c). Here it is mentioned that engine 1 does twice the amount of work as engine 2 but their individual time of doing that work is not specified. What was the kinetic energy of the film vault when it landed? var m = now.getMinutes(); (a) Kinetic energy -Law of conservation of energy states that energy can never be created or destroyed. (a) Potential energy acquired by the weights. Chapter 7 Work And Kinetic Energy Q.24P A 0.14-kg pinecone falls 16 m to the ground, where it lands with a speed of 13 m/s. When angle is {0^ \circ }. (a) Electrical Energy \to Sound Energy No work is done by the gravitational force. 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 ?. (b) becomes twice that of initial potential energy Give the meaning of each symbol which occurs in it. Sol. K.E = {1 \over 2}mv^2= {1 \over 2} \times 10(10)^2 = 500 J, Q.36 Calculate the work done by the brakes of a car of mass 1000 kg when its speed is reduced from 20 m/s to 10 m/s ? Sol. Solution: Chapter 7 Work And Kinetic Energy Q.29P (a) In the previous problem, the car’s speed decreased by 7.0 m/s as it coasted across a sandy section of road 32 m long. Sol. (e) A stretched rubber band. The upper horizontal line shows the wider range of flight speeds that would be available if Microraptor were able to produce 20 W of power. Give a reason to support your answer. How much work do you do during this time? (c) As K.E \propto \,m. (b) A person of mass 50 kg climbs a tower of height 72 metres. Q.12 On what factors does the kinetic energy of a body depend ? (d) Only potential energy (a) Work is said to be done when a force is applied on an object and the object moves due to the force. Q.106 A bulb lights up when connected to a battery. (b) Zero Kinetic energy and potential energy. When the water begins to fall, its potential energy is ... a person climbing a ladder a piece of celery blowing wind (d) Chemical Energy \to Light Energy. (c) Water stored in the reservoir of a dam. but the body will have P.E = m × g × h. (c) By what factor does the largest possible speed increase if the maximum power is doubled? III. 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. (g = 9.8 m/{s^2}) Chapter 7 Work And Kinetic Energy Q.9CQ A package rests on the floor of an elevator that is rising with constant speed. Q.50 A weightlifter is lifting weights of mass 200 kg up to a height of 2 metres. (d) a squirrel going up a tree What is the compression of the spring if the force constant of the spring is increased by a factor of four? Sol. (b) P.E = 32 J. (i) Work done = F × d = (800 + 200) × 1200 = 12 × {10^5} J. Sol. Q.9 By how much will the kinetic energy of a body increase if its speed is doubled ? Solution: Chapter 7 Work And Kinetic Energy Q.63GP The Beating Heart The average power output of the human heart is 1.33 watts. How much work is required to accelerate the car (a) from rest to the speed v0/2 and (b) from v0/2 to v0? 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. (c) Potential Energy (a) an electric bell rings Line 2 is interesting in that it has the smallest slope that still touches the power-versus-speed curve. (c) becomes 8 times that of initial kinetic energy 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. P.E = mgh where m is mass , g is accelerated due to gravity and h is height . Re searchers have produced a detailed computer simulation of Microraptor, and with its help have obtained the power-versus-speed plot presented in Figure. 2. It represents unit of energy. (c) half potential and half kinetic energy (d) less potential and more kinetic energy (c) Which law you have made use of in answering this question ? = {1 \over 2}m{v^2} - {1 \over 2}m{u^2} Calculate the work done. 10 m/{s^2}). Q.69 A stone is thrown upwards . (b) How much work do you do on the pumpkin as you carry it from the field? Solution: Chapter 7 Work And Kinetic Energy Q.46P An ice cube is placed in a microwave oven. The 62.0-kg player begins sliding 3.40 m from the base with a speed of 4.35 m/s. 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. (a) Work is measured as a product of.......and..... Q.21 What happens to the potential energy of a body when its height is doubled ? Sol. var today = day + "-" + month + "-" + now.getFullYear(); A megawatt is 1 million joules/second, and a gigawatt is 1 billion joules/second. (a). return i; Solution: a) The pitcher does positive work on the ball because the direction of force is along the direction of displacement of the ball. Solution: Chapter 7 Work And Kinetic Energy Q.80GP A 1300-kg car delivers a constant 49 hp to the drive wheels. K.E (of mass 2) = {1 \over 2}m\,(6)^2 A person is holding a bucket by applying a vertical force of 10 N. He moves it horizontally to a distance of 5 m and then climbs up a vertical distance of 10 m. Calculate the work done by him. What is its kinetic energy when it just reaches ground ? How are they related to work ? Choose all-steel Ladder Treestands for their solid construction and spacious seating. moving around it in a circular path? A simple pendulum with a bob of mass m swings with an angular amplitude of 40. = \sqrt {2 \times {{100} \over {1000}} \times 20} 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. 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. Sol. Sol. Solution: Chapter 7 Work And Kinetic Energy Q.5CQ To get out of bed in the morning, do you have to do work? Is the net force acting on the boat doing work? (b). (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. Sol. Solution: Chapter 7 Work And Kinetic Energy Q.10CQ An object moves with constant velocity. Solution: Chapter 7 Work And Kinetic Energy Q.69GP Solution: Chapter 7 Work And Kinetic Energy Q.70GP Solution: (C) If the pulling force remains the e, then the work done remains the e. If the increased mass results in a larger friction force and an increase in the pulling force, then the work done increases. How much work is done by such proteins? move down. (ii) Steam engine (g = 9.8 m/{s^2}) (c) Calculate the car’s acceleration when its speed is 28 m/s. A fraction of a second later, both hands where thrown out to his sides. A freely falling body loses potential energy , but it gains equal amount of kinetic energy such that the sum total of energy remains constant. (e) Electric bulb, Q.94 Name the devices or machines which convert : The body pushing the bicycle does work as he applies force which causes displacement. Momentum = mv = \sqrt {{m^2}{v^2}} Sol. (b) in 1 minute ? (a) Energy possessed by a body due to its motion is called its kinetic energy, A minimum of 8.1 W is needed for flight at 10 m/s. (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 : (b) How much work is done when a force of 2 N moves a body through a distance of 10 cm in the direction of force ? Solution: Chapter 7 Work And Kinetic Energy Q.22P The work W0 accelerates a car from 0 to 50 km/h. = 5 × 120 × 4 = 2400 Wh. Work done by brakes = Change in K.E. (a) What is the kinetic energy of ball when it hits the ground ? Solution: Chapter 7 Work And Kinetic Energy Q.57GP Car 1 has four times the mass of car 2, but they both have the same kinetic 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. (c). (a) 100 J (b) 600 J (c) 3600 J (d) 6000 J The man weighs 800 N and the package weighs 200 N. If g =10 m/{S^2}. (a) Does the power delivered to the apple by gravity increase, de crease, or stay the same during the time the apple falls to the ground? Q.9 By how much will the kinetic energy of a body increase if its speed is doubled ? (b) If the kayaker doubles her power output, and the resistive force due to the water remains the same, by what factor does the kayaker’s speed change? ( g = 10 m/ {s^2}) This is due to its gravitational potential energy , P.E = mgh } Sol. (b) A force of 50 N acts on a body and moves it a distance of 4 m on a horizontal surface. If the speed of car 2 is v, is the speed of car 1 equal to v/4, v/2, 2v, or 4v? (b) The pull of a moving railway engine on its coaches Others favor the “arboreal” (or trees-down) hypothesis, in which tree-dwelling animals, like modern-day flying squirrels, developed flight as an extension of gliding from tree to tree. Chemical energy \to Heat energy \to Kinetic energy of steam \to K.E of turbines \to Electrical Energy. Zero. = 2.34 × {10^9}J, Q.113 (a) Define power. Sol. No work is done when displacement is perpendicular to the direction of force. 1 kilowatt is 1,000 joules/second. Sol. Explain. 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. (i) When a body is in air and moving, it has both K.E and P.E. Q.126 In an experiment to measure his power, a student records the time taken by him in running up a flight of steps on a staircase. 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?
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