Title 6. Work, Energy and Power .pdf ✅

Work, Energy and Power 39 27. The kinetic energy acquired by a mass m in travelling distance d, starting from rest, under the action of a constant force is directly proportional to (a) m (b) m0 (c) m (d) 1 m (1994) 28. Two masses of 1 g and 9 g are moving with equal kinetic energies. The ratio of the magnitudes of their respective linear momenta is (a) 1 : 9 (b) 9 : 1 (c) 1 : 3 (d) 3 : 1 (1993) 29. A particle of mass M is moving in a horizontal circle of radius R with uniform speed v. When it moves from one point to a diametrically opposite point, its (a) kinetic energy change by Mv2 /4 (b) momentum does not change (c) momentum change by 2Mv (d) kinetic energy changes by Mv2 (1992) 6.5 Work done by a Variable Force 30. A force F = 20 + 10y acts on a particle in y-direction where F is in newton and y in meter. Work done by this force to move the particle from y = 0 to y = 1 m is (a) 20 J (b) 30 J (c) 5 J (d) 25 J (NEET 2019) 31. Force F on a particle moving in a straight line varies with distance d as shown in figure. The work done on the particle during its displacement of 12 m is F(N) (a) 18 J (b) 21 J (c) 26 J (d) 13 J (2011) 32. A body of mass 3 kg is under a constant force which causes a displacement s in metres in it, given by the relation s = t 1 3 2 , where t is in seconds. Work done by the force in 2 seconds is (a) 19 5 J (b) 5 19 J (c) 3 8 J (d) 8 3 J (2006) 33. A force F acting on an object varies with distance x as shown here. The force is in N and x in m. The work done by the force in moving the object from x = 0 to x = 6 m is (a) 18.0 J F(N) (b) 13.5 J (c) 9.0 J (d) 4.5 J. (2005) 34. A force acts on a 3 g particle in such a way that the position of the particle as a function of time is given by x = 3t – 4t 2 + t 3 , where x is in metres and t is in seconds. The work done during the first 4 second is (a) 490 mJ (b) 450 mJ (c) 240 mJ (d) 530 mJ (1998) 35. A position dependent force, F = (7 – 2x + 3x2 ) N acts on a small body of mass 2 kg and displaces it from x = 0 to x = 5 m. The work done in joule is (a) 135 (b) 270 (c) 35 (d) 70 (1994, 1992) 6.7 The Concept of Potential Energy 36. The potential energy of a particle in a force field is U A r B r = − 2 where A and B are positive constants and r is the distance of the particle from the centre of the field. For stable equilibrium, the distance of the particle is (a) B 2A (b) 2A B (c) A B (d) B A (2012) 37. The potential energy of a system increases if work is done (a) upon the system by a nonconservative force (b) by the system against a conservative force (c) by the system against a nonconservative force (d) upon the system by a conservative force. (2011) 38. The potential energy between two atoms, in a molecule, is given by U x a x b x ( ) = − 12 6 where a and b are positive constants and x is the distance between the atoms. The atom is in stable equilibrium, when (a) x a b =       2 1 6 (b) x a b =       11 5 1 6 (c) x = 0 (d) x a b =       2 1 6 (1995) 6.8 The Conservation of Mechanical Energy 39. A mass m is attached to a thin wire and whirled in a vertical circle. The wire is most likely to break when (a) inclined at an angle of 60° from vertical (b) the mass is at the highest point (c) the wire is horizontal (d) the mass is at the lowest point (NEET 2019) 40. A body initially at rest and sliding along a frictionless track from a height h (as shown in the figure) just completes a vertical circle of diameter AB = D. The height h is equal to (a) 3 2 D (b) D (c) 7 5 D (d) 5 4 D (NEET 2018) EduHulk.COM