Use coulomb's law, f=kq1q2/d2, to calculate the electric force on an electron (q=−1.6×10−19c) exerted by a single proton if the particles are 0.53×10−10m apart. the constant k in coulomb's law is 9.0×109 n⋅m2/c2. (the unit abbreviated n is the newton, the si unit of force.) express your answer using two significant figures.

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.