JEE Mains Morning Question 12th Jan Paper 2019 Physics Part 1 Download all the papers for 2019 Exam

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Q-1 Two light identical springs of spring constant k are attached horizontally at the two ends of a uniform horizontal rod AB of length and mass m. the rod is pivoted at its centre ‘O’ and can rotate freely in horizontal plane. The other ends of the two springs are fixed to rigid supports as shown in figure. The rod is gently pushed through a small angle and released. The frequency of resulting oscillation is:

Identical springs of spring constant.

Identical Springs of Spring Constant.

Identical springs of spring constant.

Options:-

1.

2.

3.

4.

Answer: 1

Explanation:-

Rod is pivoted

Rod is Pivoted

Rod is pivoted

From figure

And

So,

Q-2 A cylinder of radius R is surrounded by a cylindrical shell of inner radius R and outer radius 2R. The thermal conductivity of the material of the inner cylinder is and that of the outer cylinder is . Assuming no loss of heat, the effective thermal conductivity of the system for heat flowing along the length of the cylinder is:

Options:-

1.

2.

3.

4.

Answer: 4

Explanation:-

Cylinder

Cylinder

Cylinder

Both are in parallel combination

Q-3 A travelling harmonic wave is represented by the equation where x and y are in meter and t is in seconds. Which of the following is a correct statement about the wave?

The wave is propagating along the

Options:-

1. Negative x-axis with speed

2. The wave is propagating along the positive x-axis with speed

3. The wave is propagating along the positive x-axis with speed

4. The wave is propagating along the negative x-axis with speed

Answer: 1

Explanation:-

Wave speed

Where in

General

Wave is moving along

-ve x-axis with speed V

And

Q-4 A Straight rod of length L extends from x=a to x=L+a. the gravitational force is exerted on a point mass ‘m’ at x=0, if the mass per unit length of the rod is , is given by:

Options:-

1.

2.

3.

4.

Answer: 2

Explanation:-

Straight rod of length L

Straight Rod of Length L

Straight rod of length L

Force is along the line joining the two masses

Assume dx element at a distance x from x=0

So,

Developed by: