A body of mass 5 kg resting on a smooth horizontal plane, is acted upon

Explanation

(a) Resultant of the forces acting on the plane = (6i + 2j) + (5i + 4j) + (4i - j) = 15i + 5j

\(F = \frac{m \Delta v}{t}\)

Resultant force = \(\frac{mv}{t} \)

\(15i + 5j = \frac{5v}{t}\)

\(v = \frac{(15i + 5j). t}{5} = 3t i + t j\)

(b) velocity after 4 seconds = \(3(4) i + 4 j = 12 i + 4 j\)

\(\therefore |12i + 4j| = \sqrt{12^{2} + 4^{2}} = \sqrt{144 + 16}\)

= \(\sqrt{160} \)

= \(4\sqrt{10} m/s\)