JEE Main 2025 Apr 8 Shift 2, Physics Q15: Newton's Laws Of Motion

JEE Main2025Apr 8, Shift 2Physics

A body of mass 2 kg moving with velocity of $v_{in} = 3 \hat{i} + 4 \hat{j}$ ms $^{- 1}$ enters into a constant force field of 6 N directed along positive z-axis. If the body remains in the field for a period of $\frac{5}{3}$ seconds, then velocity of the body when it emerges from force field is

A
$4 \hat{i} + 3 \hat{j} + 5 \hat{k}$
B
$3 \hat{i} + 4 \hat{j} + 5 \hat{k}$
C
$3 \hat{i} + 4 \hat{j} - 5 \hat{k}$
D
$3 \hat{i} + 4 \hat{j} + 5 \hat{k}$

Solution

The applied force acts only along $+ \hat{k}$ , so the x and y components of velocity remain unchanged; only $v_{z}$ changes.

Acceleration in the z-direction: $a = \frac{F}{m} = \frac{6}{2} = 3$ m/s $^{2}$ along $+ \hat{k}$ .

Change in $v_{z}$ : $Δ v_{z} = a t = 3 \times \frac{5}{3} = 5$ m/s.

Final velocity: $v = 3 \hat{i} + 4 \hat{j} + 5 \hat{k}$ m/s, matching option (2).

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JEE Main 2025 Apr 8 Shift 2, Physics Q15: Newton's Laws Of Motion

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