As the density of water = p = 103 kg m-3 Determine the work done on the car. An electron and a proton are detected in a cosmic ray experiment, the first with kinetic energy 10 keV, and the second with 100 keV. The x-component of momentum of molecule, Question 6. Answer: Here m = 0.5 kg (b) Here P.E. (b) Comets move around the sun in highly elliptical orbits. Read the problem carefully and develop a mental picture of the physical situation. η=p0/pi=> pi=p0/η = 13070/(30/100)=43567 W =43.56 KW. The gravitational force on the comet due to the sun is not normal to the comet’s velocity in general. B. 1. (c) Here x = 0 to x = a and x > b, the P.E. =>p0=(30 x 103 x 9.8 x 40)/900=13070 watt (d) Change in kinetic energy of the body in 10 s and interpret your results. Therefore, all other curves cannot possibly describe the elastic collision of two billiard balls. Two inclined frictionless tracks, one gradual and the other steep meet at A from where two stones are allowed to slide down from rest, one on each track (Fig). How high does the bob A rise after the collision? cannot possibly describe the elastic collision of two billiard balls? At maximum compression, the box has a speed of zero. Understanding the concept of power High School Physics - Electrical Energy and Power Initial velocity at x = 0, v1 = a x 0 = 0 Clearly, the system is not being acted upon by an external force. The bob of a pendulum is released from a horizontal position. Question 6. Using law of conservation of momentum. Which is faster, the electron or the proton? 30. How much fat will the dieter use up? A bullet of mass 0.012 kg and horizontal speed 70 ms-1 strikes a block of wood of mass 0.4 kg and instantly comes to rest with respect to the block. Question 6. a) Determine the maximum compression of the spring. Work done by the gravitational ‘ force of the sun over a closed path in every complete orbit of the comet is zero. NCERT Solutions for Class 11 Physics Chapter 6 Work Energy and power are part of NCERT Solutions for Class 11 Physics. Find the coefficient of friction between the block and the incline. If the length of the pendulum is 1.5 m, what is the speed with which the bob arrives at the lowermost point, given that it dissipated 5% of its initial energy against air resistance? Hence. What is the speed of the trolley after the entire sand bag is empty? becomes zero i.e., at r = R + R = 2 R; V (r) = 0. (b)Work done by a body against friction always results in a loss of its kinetic/potential energy. Show that the two body decay of this type must necessarily give an electron of fixed energy, and therefore, cannot account for the observed continuous energy distribution in the β -decay of a neutron or a nucleus, Fig. A particle of mass 0.5 kg travels in a straight line with velocity u = a x3/2, where a = 5 m-1/2 s-1. A trolley of mass 300 kg carrying a sandbag of 25 kg is moving uniformly with a speed of 27 km/h on a friction less track. Give reasons for your answer. A raindrop of radius 2 mm falls from a height of 500 m above the ground. The block is released from rest with the spring in the unstretched position. A person trying to lose weight (dieter) lifts a 10 kg mass, one thousand times, to a height of 0.5 m each time. = work done by the net force in 10 seconds = 635.04 J (This is in accordance with work-energy theorem). Thus the particle cannot be present in the region x > a. Introduction to work and energy Our mission is to provide a free, world-class education to anyone, anywhere. Final speed of trolley is 10.36 ms-1. is dissipated against air resistance, the balance 95% energy is transformed into K.E. Answer: Here, m = 10 kg, h = 0.5 m, n = 1000 Question 6. The bolt does not rebound. What is the work done by this force in moving the body a distance of 4 m along the z-axis? (c) Work done by friction on a body sliding down an inclined plane, (b) Total energy of a system is always conserved, no matter what internal and external forces on the body are present. Mass of rain drop = volume of drop x density The bob A of a pendulum released from 30° to the vertical hits another bob B of the same mass at rest on a table as shown in Fig. Answer: (a) False, the total momentum and total energy of the system are conserved. θ = 90°. Answer: Let m be the mass of each ball bearing. Whence Δv =mu/ M + m Question 6. 20. Work and energy can be considered as two sides of the same coin. Question 6. Part (b): Edexcel Mechanics M2 January 2012 Q3b : ExamSolutions - youtube Video. = 0.1623 joule. Putting values Δv =4 x 20/ 20 + 220 = ms-1 Solution : Work : W = m g h = (60)(10)(5) = 3000 Joule. Answer: (a) Potential energy of the body decreases because the body in this case goes closer to the centre of the force. (c) Work done in the motion of a body over a closed loop is zero for every force in nature. Solutions and Problems(work,energy and power) work energy and power problems with solution work enegy power exam physics work and energy exam problems work, energy, power exam work power energy exam 1and problem solutons work energy problem with solution problem solutions on work and energy works , power and problems and solustions (c) Work done by net force = 5.04 x 126 = 635.04 J (d) Work done by an applied force on a body moving on a rough horizontal plane with uniform velocity, (Note, we are talking here of potential energy corresponding to the force during collision, not gravitational potential energy). Answer: Here, r = 2 mm = 2 x 10-3 m. Whe... Problem#1 The electric flux through a certain area of a dielectric is (8.76 x 10 3 Vm/s 4 ) t 4 . 3. Is the collision elastic or inelastic? (i) t1/2 (ii) t (iii) t3/2 (iv) t2 13. So there shall be no change in the speed of the trolley. The total energy of the particle is indicated by a cross on the ordinate axis. 19. A molecule in a gas container hits a horizontal wall with speed 200 msA and angle 30° with the normal, and rebounds with the same speed. The block moves 10 cm down the incline before coming to rest. Case II, E2 = 1/2 mv2 If 20% of this energy can be converted to useful electrical energy, how large an area is needed to supply 8 kW? Which of the following potential energy curves in Fig. Sunday, January 19, 2020 Add Comment Edit. .’. 2) View Solution. = 0.76 x107 J/kg =1/2mv2 + 0 =1/2 mv2 Note: Whether the drop moves with decreasing acceleration or with uniform speed, work After collision, K.E. It is related to energy, which is the quantity used to measure work. Work done by the resistive forces, W =E1 – E2 = 0.164 – 1.675 x 10-3 W (i), force is applied on the mass, by the man in vertically upward direction but distance is moved along the horizontal. The child take 2.5 s to run on the trolley. What is the electrical power produced? Identify the known and unknown quantities in an organized manner. A high-speed camera records this even... Problem#1 A ballet dancer has a moment of inertia of 4 kg.m 2 when his arms reach his body and 16 kg.m 2 when his arms are stretched. Answer: Here, volume of water = 30 m3 ; t = 15 min = 15 x 60 = 900s The particle can not exist in these portions. (c) The rate of change of total momentum of a many-particle system is proportional to the external force/sum of the internal forces of the system. Answer the following: So the whole of the energy is converted into heat. 75 kJ. Its displacement in time t is proportional to (i) t1/2 (ii) t (iii) t3/2 (iv) t2 Final velocity at x = 2, v2 = a (2)3/2 = 5 x (2)3/2 Power : P = W / t = 3000 / 10 = 300 Joule/se cond. (1 hp = 746W. acceleration = 5.04/2 ms-2 = 2.52 ms-2 23. In which case is the work done greater? Initial speed (v o) = 0 m/s (car rest) Final speed (v t) = 20 m/s. In each case, specify the regions, if any, in which the particle cannot be found for the given energy. Work, Energy and Power: Audio Guided Solution Problem 1: Renatta Gass is out with her friends. Known : Power (P) = 300 Watt = 300 Joule/second. Answer: (a) Heat energy required for burning of casing of rocket comes from the rocket itself. Question 6. © 1996-2020 The Physics Classroom, All rights reserved. Period (T) = 5 minutes = 5 (60 seconds) = 300 seconds. Answer carefully, with reasons: Home › Energy and Energy Transfer Problems and Solutions › Problems and Solutions Work Power and Energy. Answer: (a) Power used by family, p = 8 KW = 8000 W (a) Work done ‘positive’, because force is acting in the direction of displacement i.e., θ = 0°.