A particle moves with constant acceleration. Its velocity is (7i+j)(7\mathbf{i}+\mathbf{j})(7i+j) m s−1^{-1}−1 when t=2t=2t=2 s and (−i+9j)(-\mathbf{i}+9\mathbf{j})(−i+9j) m s−1^{-1}−1 when t=6t=6t=6 s. At time t=0t=0t=0, its position vector is (3i−4j)(3\mathbf{i}-4\mathbf{j})(3i−4j) m.
Find the acceleration of the particle.
Find its velocity when t=0t=0t=0.
Find its position vector when t=5t=5t=5 s.
Find the time at which the velocity is parallel to j\mathbf{j}j, and state the velocity at this time.