1
JEE Main 2021 (Online) 17th March Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
When two soap bubbles of radii a and b (b > a) coalesce, the radius of curvature of common surface is :
A
$${{b - a} \over {ab}}$$
B
$${{a + b} \over {ab}}$$
C
$${{ab} \over {a + b}}$$
D
$${{ab} \over {b - a}}$$
2
JEE Main 2021 (Online) 17th March Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
A car accelerates from rest at a constant rate $$\alpha$$ for some time after which it decelerates at a constant rate $$\beta$$ to come to rest. If the total time elapsed is t seconds, the total distance travelled is :
A
$${{4\alpha \beta } \over {(\alpha + \beta )}}{t^2}$$
B
$${{2\alpha \beta } \over {(\alpha + \beta )}}{t^2}$$
C
$${{\alpha \beta } \over {2(\alpha + \beta )}}{t^2}$$
D
$${{\alpha \beta } \over {4(\alpha + \beta )}}{t^2}$$
3
JEE Main 2021 (Online) 17th March Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
A mass M hangs on a massless rod of length l which rotates at a constant angular frequency. The mass M moves with steady speed in a circular path of constant radius. Assume that the system is in steady circular motion with constant angular velocity $$\omega$$. The angular momentum of M about point A is LA which lies in the positive z direction and the angular momentum of M about point B is LB. The correct statement for this system is :

JEE Main 2021 (Online) 17th March Morning Shift Physics - Rotational Motion Question 86 English
A
LA is constant, both in magnitude and direction
B
LB is constant in direction with varying magnitude
C
LB is constant, both in magnitude and direction
D
LA and LB are both constant in magnitude and direction
4
JEE Main 2021 (Online) 17th March Morning Shift
MCQ (Single Correct Answer)
+4
-1
Change Language
A solenoid of 1000 turns per metre has a core with relative permeability 500. Insulated windings of the solenoid carry an electric current of 5A. The magnetic flux density produced by the solenoid is : (permeability of free space = 4$$\pi$$ $$\times$$ 10$$-$$7 H/m)
A
$$\pi$$T
B
2 $$\times$$ 10$$-$$3$$\pi$$ T
C
10$$-$$4$$\pi$$ T
D
$${\pi \over 5}$$ T
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