Ablock of mass 4.0 kg rests on a horizontal surface where the coefficient of kinetic friction between the two is 0.20. a string attached to the block is pulled horizontally, resulting in a 3.0-m/s2 acceleration by the block. find the tension in the string. (g = 9.80 m/s2)

Asailboat is traveling to the right when a gust of wind causes the boat to accelerate leftward at 2.5m/s2 for 4s. after the wind stops, the sailboat is traveling to the left with a velocity of 3.0m/s.assuming the acceleration from the wind is constant, what was the initial velocity of the sailboat before the gust of wind? answer using a coordinate system where rightward is positive.