The initial velocity of a particle is u=(4i^+3j^)  ms-1. It is moving with uniform acceleration a=(0.4i^+0.3j^) ms−2. The magnitude of its velocity after 10 s is

v=u+at =(4i^+3j^)+(0.4i^+0.3j^)×10 =(8i^+6j^) ms−1The x and y components of velocity are vx = 8 ms-1 and vy= 6 ms-1. The magnitude of velocity v=vx2+vy2=(8)2+(6)2=10 ms−1