3-2.Motion in Plane
hard

The projectile motion of a particle of mass $5\, g$ is shown in the figure.
The initial velocity of the particle is $5 \sqrt{2}\, ms ^{-1}$ and the air resistance is assumed to be negligible. The magnitude of the change in momentum between the points $A$ and $B$ is $x \times 10^{-2}\, kgms ^{-1} .$ The value of $x ,$ to the nearest integer, is ...... .

A$10$
B$8$
C$3$
D$5$
(JEE MAIN-2021)

Solution

$|\overrightarrow{ u }|=|\overrightarrow{ v }|…..(1)$
$\overrightarrow{ u }=u \cos 45 \hat{ i }+ u \sin 45 \hat{ j }…..(2)$
$\overrightarrow{ v }= v \cos 45 \hat{ i }- v \sin 45 \hat{ j }…..(3)$
$|\overrightarrow{\Delta P }|=| m (\overrightarrow{ v }-\overrightarrow{ u })|…..(4)$
$\Delta P =2 mu \sin 45^{\circ}$
$=2 \times 5 \times 10^{-3} \times 5 \sqrt{2} \times \frac{1}{\sqrt{2}}$
$=50 \times 10^{-3}$
$=5 \times 10^{-2}$
Standard 11
Physics

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