Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Work Energy and Power question

2015 · Q139
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /NEET
  3. /Physics
  4. /Work Energy and Power
  5. /2015 · Q139

Work Energy and Power question

2015 · Q139

NEETPhysicsWork Energy and PowerMCQ+4 / −1
A block of mass 10 kg, moving in x direction with a constant speed of 10 m s−-−1, is subjected to a retarding force F = 0.1x J/m during its travel from x = 20 m to 30 m. Its final KE will be
  1. A
    275 J
  2. B
    250 J
  3. C
    475 J
  4. D
    450 J
View written solutionFree

Correct answer: C

Here, m = 10 kg, vi = 10 ms–1
Initial kinetic energy of the block is
Ki=12mvi2=12×(10 kg)×(10 ms−1)2=500 J{K_i} = {1 \over 2}mv_i^2 = {1 \over 2} \times \left( {10\,kg} \right) \times {\left( {10\,m{s^{ - 1}}} \right)^2} = 500\,JKi​=21​mvi2​=21​×(10kg)×(10ms−1)2=500J

Work done by retarding force

W=∫x1x2Frdx=∫2030−0.1 xdx=−0.1[x22]2030W = \int\limits_{{x_1}}^{{x_2}} {{F_r}dx = \int\limits_{20}^{30} { - 0.1\,xdx = - 0.1} \left[ {{{{x^2}} \over 2}} \right]} _{20}^{30}W=x1​∫x2​​Fr​dx=20∫30​−0.1xdx=−0.1[2x2​]2030​

=−0.1[900−4002]=−25 J = - 0.1\left[ {{{900 - 400} \over 2}} \right] = - 25\,J=−0.1[2900−400​]=−25J

According to work-energy theorem,

W = Kf – Ki

Kf = W + Ki = – 25 J + 500 J = 475 J

PreviousNext

More from Work Energy and Power

  • A particle of mass m is driven by a machine that delivers a constant power k watts. If the particle starts from rest the force on the particle at time t is2015 · MCQ
  • Two similar springs P and Q have spring constants KP and KQ, such that KP > KQ. They are stretched first by the same amount (case a), then by the same force (case b). The work done by the springs WP and WQ are related as, in case (a)…2015 · MCQ
  • A particle with total energy E is moving in a potential energy region U(x). Motion of the particle is restricted to the region when2013 · MCQ
  • One coolie takes 1 minute to raise a suitcase through a height of 2 m but the second coolie takes 30 s to raise the same suitcase to the same height. The powers of two coolies are in the ratio2013 · MCQ
  • A uniform force of (3i+j​) newton acts on a particle of mass 2 kg. Hence the particle is displaced from position (2i+k) metre to position (4i+3j​−k)…2013 · MCQ
  • A car of mass m starts from rest and accelerates so that the instantaneous power delivered to the car has a constant magnitude P0. The instantaneous velocity of this car is proportional to2012 · MCQ
  • A solid cylinder of mass 3 kg is rolling on a horizontal surface with velocity 4 m s−1. It collides with a horizontal spring of force constant 200 N m−1. The maximum compression produced in the spring will be2012 · MCQ
  • The potential energy of a particle in a force field is U=r2A​−rB​ where A and B are positive constants and r is the distance of particle from the centre of the field. For stable equilibrium, the distance of the…2012 · MCQ