JEE Main 2021 (Online) 27th July Morning Shift | Properties of Matter Question 148 | Physics

A body takes 4 min. to cool from 61$$^\circ$$ C to 59$$^\circ$$ C. If the temperature of the surroundings is 30$$^\circ$$ C, the time taken by the body to cool from 51$$^\circ$$ C to 49$$^\circ$$ C is :

4 min.

3 min.

8 min.

6 min.

JEE Main 2021 (Online) 25th July Evening Shift

MCQ (Single Correct Answer)

-1

Two spherical soap bubbles of radii r₁ and r₂ in vacuum combine under isothermal conditions. The resulting bubble has a radius equal to :

$${{{r_1}{r_2}} \over {{r_1} + {r_2}}}$$

$$\sqrt {{r_1}{r_2}} $$

$$\sqrt {r_1^2 + r_2^2} $$

$${{{r_1} + {r_2}} \over 2}$$

JEE Main 2021 (Online) 25th July Morning Shift

MCQ (Single Correct Answer)

-1

Two wires of same length and radius are joined end to end and loaded. The Young's modulii of the materials of the two wires are Y₁ and Y₂. The combination behaves as a single wire then its Young's modulus is :

$$Y = {{2{Y_1}{Y_2}} \over {3({Y_1} + {Y_2})}}$$

$$Y = {{2{Y_1}{Y_2}} \over {{Y_1} + {Y_2}}}$$

$$Y = {{{Y_1}{Y_2}} \over {2({Y_1} + {Y_2})}}$$

$$Y = {{{Y_1}{Y_2}} \over {{Y_1} + {Y_2}}}$$

JEE Main 2021 (Online) 20th July Evening Shift

MCQ (Single Correct Answer)

-1

The length of a metal wire is l₁, when the tension in it is T₁ and is l₂ when the tension is T₂. The natural length of the wire is :

$$\sqrt {{l_1}{l_2}} $$

$${{{l_1}{T_2} - {l_2}{T_1}} \over {{T_2} - {T_1}}}$$

$${{{l_1}{T_2} + {l_2}{T_1}} \over {{T_2} + {T_1}}}$$

$${{{l_1} + {l_2}} \over 2}$$