In one of the exercises to strengthen the wrist and fingers, a person squeezes and releaases a soft rubber ball. Is the work done on the ball positive, negative or zero during compression? During expansion?

These questions consists of two statements each printed as Assertion and Reason. While answering these question you are required to choose any one of the following five reponses (a) If both Assertion and Reason arecorrect and Reason is the correct explanation of Asserrtion. (b) If both Assertion and Reason are correct but Reason is not the correct explanation of Assertion. (c ) If Assertion is true but Reason is false. (d) If Assertion is false but Reason is true. Assertion Total work done by spring may be positive ,negative or zero. Reason Direction of spring force is always towards mean position.

During isothermal expansion at 800 K, the working substance of a Carnot's engine extracts 480 cal of heat. If the sink be at 300 K, calculate (i) the work done by the working substance during isothermal expansion (ii) the work done on the substance during isothermal compression (iii) the efficiency of the ideal engine.

A ball of mass m is moved with speed v_0 at the highest point in a closed circular tube of radius R kept in the vertical plane. The cross-section of the tube is such that the block just fits in it. The block makes several oscillations inside the tube and finally stops at the lowest point. Find the work done by the tube on the block during the process.

The work done during expansion of a gas in vacuum is zero, because there is

In the previous illustration. Consider the situation when the string is completely compressed. Then it begins to relax and will come to its original length. a. What is the work done by the spring during the period? b. Is the work done by the spring positive or negative?

A plank of mass M and length L is placed at rest on a smooth horizontal surface A small block of mass m is projected wii:h a velocity v_(0) as shown in the Fig. 3.31 (a), The coefficient of friction between the block and the plank is mu , plank is very long so that block eventually comes to rest on it. (i) Find the work done by the ftjctioh force on the block during the period it slides on the plank. Is the Work positive or negative ?' (ii) Calculate the work done on the plank during the same period. Is the work positive or negative? (iii) Also, determine the net work done by friction. Is it positive or negative ?

Gravitational force is a conservation and medium independent force. Its nature is attractive. Gravitational field intensity and gravitational potential gives information about gravitational fied in vector and scaler form respectively. Actually gravitational fied intensity is equal to the negative of the negative of teh potential gradient. potential energy is defined for only conservation force. it is also equal to the total energy in escaping condition. gravitational potential is either negative or zero but can never be positive due to attractive nature of gravitational force. A person brings a mass of 1 kg from infinity to a point A . Initially the mass was at rest but it moves with a speed of 2 m//s as it reaches A . The work done by the person on a mass is -3 J . The potential of A is:

An adiabatic vessel of total volume V is divided into two equal parts by a conducting separtor. The is fixed in this position. The part on the left contains one mole of an ideal gas (U=1.5 nRT) and the part on the right contains two moles of the same gas. initially, the pressure on each side is p. the system is left for sufficiant time so that a steady state is reached. find (a) the work done by the gas in the left part during the process, (b) the temperature on the two sides in the beginning, (c ) the final common temperature reached by the gases, (d) the heat given to the gas in the right part and (e) the increase in the internal energy of the gas in the left part.