Determinate the velocity (magnitude and direction) of the disk at t=1.5s after the force is applied?

Question

A 0.4kg disk is sliding on a smooth horizontal surface with an initial velocity of v=3i +4j m/s when a force F=5i N is suddently applied to the disk.

Answer 1

v = (3i + 4j) + 5i * 1.5 / 0.4

= 21.75i + 4j.

Magnitude sqrt(21.75^2 + 4^2)

= 22.1 m/s.

Direction makes angle t with direction of vector i, where:

tan(t) = 4 / 21.75

t = 10.4 deg.