A particle has an initial velocity of 3i + 4j and an acceleration of 0.4i + 0.3j. Its speed after 10s is

- 7(√2) units
- 10 units
- 7 units
- 8.5 units

**Solution**

Use equation of kinematics: v = u + at

Initial Velocity, u = 3i + 4j

Acceleration, a = 0.4i + 0.3j

Time, t = 10s

v = (3i + 4j) + 10(0.4i + 0.3j)

v = (3i + 4j) + (4i + 3j)

v = 7i + 7j

|v| = √(7^{2}+7^{2}) = 7(√2)

**Correct option is A.**