# IIT JEEE Physics - 1986

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### IIT JEE –Past papers:

IIT JEE –Past papers PHYSICS- UNSOLVED PAPER - 1986

### SECTION – I:

SECTION – I Single Correct Answer Type In each of the statements given below, several alternatives are given. In some cases, more than one alternative is correct. Select the correct alternative (s) in each case and write down the corresponding letter (s) (a), (b), (c) or (d) in your answer pf book. For each part, marks will be awarded only if ALL the correct alternatives are selected and written:

### Problem:

01 The dimensions of the quantities in one (or more) of the following pairs are the same. Identify the pair (s). Torque and work Angular momentum and work Energy and young’ s modules Light-year and wavelength. Problem

### Problem:

Problem 02 A ball hits the floor and rebounds after an inelastic collision. In this case: The momentum of the ball just after the collision is the same as that just before the collision. The total momentum energy of the ball remains the same in the collision. The total momentum of the ball and the earth is conserved. The total energy of the ball and the earth is conserved.

### Problem:

Problem 03 A shell is fired from cannon with a velocity V (m/s) at an angle with the horizontal direction. At the highest point in its path, it explodes into pieces of equal masses. One of the pieces retraces its path to the cannon and the speed (in m/s) of the other piece immediately after the explosion is: 3 V cos b. 2 V cos c. d.

### Problem:

Problem 04 A reference frame attached to the earth Is an inertial frame by definition Cannot be an inertial frame because the earth is revolving around the sun. Is an inertial frame because Newton’s laws are applicable in this frame. Cannot be an inertial frame because the earth is rotating about its own axis.

### Problem:

Problem 05 A simple pendulum of length L and mass (bob) M is oscillating in a plane about a vertical line between angular limits - and + . For an angular displacement the tension in the string and the velocity of the bob are T and V respectively. The following relations hold good under the above conditions: a. b. c. The magnitude of the tangential acceleration of the bob d.

### Problem:

Problem 06 Steam at 100 0 C is passed into 1.1 kg of water contained in a calorimeter of water equivalent 0.02kg at 15 0 C, till the temperature of the calorimeter and its contents rises to 80 0 C. The mass of the steam condensed in kilogram is 0.130 0.065 0.260 0.135

### Problem:

Problem 07 Two thin long parallel wires separated by a distance b are carrying a current i each. The magnitude of the force per unit length exerted by one wire on the other is a. b. c. d.

### Problem:

Problem 08 A converging lens is used to form an image on a screen. When the upper half of the lens is covered by opaque screen Half the image will disappear Complete image will be formed Intensity of the image will increase Intensity of the image will decrease

### Problem:

Problem 09 A tube, close at a one end and containing air, produces, when excited, the fundamental note of frequency 512 Hz. If the tube is open at both ends the fundamental frequency that can be excited is (in Hz). 1024 512 256 128

### Problem:

Problem 10 The mass number of a nucleus is Always less than its atomic number. Always more than its atomic number. Sometimes equal to its atomic number. Sometimes more than and sometimes equal to atomic number.

### SECTION – II:

SECTION – II Fill in the blanks Read the statements carefully. Indicate the sub-division number and write down the matter corresponding to each blank strictly in the order in which it appears in the statement.

### Problem:

01 When the number of electrons striking the anode of an X-ray tube is increased, the _________ of the emitted X-rays increases, while when the speeds of the electrons striking the anode are increased, the cut-off wavelength of emitted X rays_________. Problem

### Problem:

Problem 02 In Young’s double-slit experiment, the two slits act as coherent sources of equal amplitude A and of wavelength In another experiment with same set-up the two slits are sources of equal amplitude A and wavelength but are incoherent. The ratio of the intensity of light at the midpoint of the screen in the first case to that in the second case is _______________.

### Problem:

Problem 03 Two small balls having equal positive charges Q(C) on each are suspended by two insulating strings of equal length L(m) from a hook fixed to a stand. The whole set up is taken in a satellite into space where there is no gravity (state of weightlessness.), The angle between the two strings is _________ and the tension in each string is ____________ N.

### Problem:

Problem 04 Two simple harmonic motions are represented by the equations and Their amplitudes are in the ratio of___________

### Problem:

Problem 05 When Boron nucleus ( B) is bombarded by neutrons, -particles are emitted. The resulting nucleus is of the element __________ and has the mass number__________

### Problem:

Problem 06 Atoms having the same ______________ but different _____________ are called isotopes.

### SECTION – III:

SECTION – III Each of which either true or False State whether the following statements are TRUE or FALSE, giving reasons in brief to support your answer. No marks will be awarded if correct reasons are not given .

### Problem:

01 Two protons A and B are placed in between the two plates of a parallel plate capacitor charged to a potential difference V as shown in Fig.1986.1. The forces on the two protons are identical. Problem

### Problem:

Problem 02 In a photoelectric emission process, the maximum energy of the photoelectrons increases with increasing intensity of the incident light.

### Problem:

Problem 03 A block of ice with a lead shot embedded in it is floating on water contained in a vessel. The temperature of the system is maintained at 0 0 C as the ice melts. When the ice melts completely, the level of water in the vessel rises.

### Problem:

Problem 04 A coil of metal wire is kept stationary in a non-uniform magnetic field. An emf is induced in the coil.

### Problem:

Problem 05 A thin uniform circular disc of mass M and radius R is rotating in a horizontal plane about an axis passing through its center and perpendicular to its plane with an angular velocity . Another disc of the same dimension but of mass M/4 is placed gently on the first disc coaxially. The angular velocity of the system now is .

### Problem:

Problem 06 For a diode, the variation of its anode current with the anode voltage at two different cathode temperature and is shown in Fig. 1986.2. The temperature is greater than .

### Slide 27:

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