A particle has initial velocity (3î + 4ĵ) and

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A particle has initial velocity (3î + 4ĵ) and has acceleration (0.4 î + 0.3 ĵ). It's speed after 10 s is:

1. 7 units
2. 7√2 units
3. 8.5 units
4. 10 units

Correct Option: B

^→u = 3î + 4ĵ,^→a = 0.4î + 0.3ĵ
⇒ u_x = 3 units, u_y = 4 units
a_x = 0.4 units, a_y = 0.3 units
∴ v_x + a_x × 10 = 3 + 4 = 7 ms^–1
and v_y = 4 + 0.3 × 10 = 4 + 3 = 7 ms^–1
∴ v = √v_x² + v_y²
= 7√2 ms^–1