Answer these questions

15. A. three-quarter of mass 80 kg is running at 5 m 51. An opponent pushes him with a constant force so that 1% 3 later he is moving at the same speed in a direction making 26 with his original direction of motion. How large is this force?' ' 16. A boat of mass 300 kg moving at a constant Velocity of 3 m 51 NE enters a current which exerts a force on it of 90 newtons SE. Find its velocity 10 3 later. ' 17. An electron of mass 9 X 10\"31 kg is moving at 8 x 10\" m 51 when it enters an electric eld which produces a force of 1-8 x 1015 N at right angles to its initial direction of motion for-a period of 3 x 10-9 s. Find its nal velocity. (Neglect the small variation in mass of the electron with its speed.)