A small particle of mass m moving inside a heavy, hollow and straight tube along the tube axis, undergoes elastic collision at two ends. The tube has no friction and it is closed at one end by a flat surface while the other end is fitted with a heavy movable flat piston as shown in figure. When the distance of the piston from closed end is L = L 0 the particle speed is v = v 0 . The piston is moved inward at a very low speed V such that V ≪ d L L v 0 , where d L is the infinitesimal displacement of the piston. Which of the following statement(s) is/are correct?

The particle's kinetic energy increases by a factor of 4 when the piston is moved inward from L 0 to 1 2 L 0

The rate at which the particle strikes the piston is v L

If the piston moves inward by d L , the particle speed increases by 2 v d L L

A thin and uniform rod of mass M and length L is held vertical on a floor with large friction. The rod is released from rest so that it falls by rotating about its contact-point with the floor without slipping. Which of the following statement(s) is/are correct, when the rod makes an angle 60 o with vertical? [ g is the acceleration due to gravity]

The normal reaction force from the floor on the rod will be M g 16

The angular acceleration of the rod will be 2 g L

A particle of mass m is initially at rest at the origin. It is subjected to a force and starts moving along the x - axis. Its kinetic energy changes with time as d K d t = γ t , where γ is a positive constant of appropriate dimensions. Which of the following statements is (are) true?

The distance of the particle from the origin increases linearly with time

E M B I B E

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 5 - Work, Energy and Power>JEE Advanced Paper 2 - 2014>Q 5

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JEE Advanced

IMPORTANT

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A tennis ball is dropped on a horizontal smooth surface. It bounces back to its original position after hitting the surface. The force on the ball during the collision is proportional to the length of compression of the ball. Which one of the following sketches describes the variation of its kinetic energy $K$ with $t$ time most appropriately? The figures are only illustrative and not to the scale.

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Important Questions on Work, Energy and Power

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JEE Advanced

IMPORTANT

EMBIBE CHAPTER WISE PREVIOUS YEAR PAPERS FOR PHYSICS>Chapter 5 - Work, Energy and Power>JEE Advanced Paper 2 - 2014>Q 6

A wire, which passes through the hole in a small bead, is bent in the form of quarter of a circle. The wire is fixed vertically on ground as shown in the figure. The bead is released from near the top of the wire and it slides along the wire without friction. As the bead moves from A to B, the force it applies on the wire is

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