(a)The raindrop continues to fall at the same rate. As a result, the acceleration will be zero. Because F = ma, the force exerted on the drop will be zero when the acceleration is zero.

(b) The cork floats on water, implying that the upthrust balances the cork’s weight. As a result, there will be no net force on the cork.

(c) Because the automobile is moving at a constant speed, the acceleration is zero. As a result, there will be no force.

(d) Because the high-speed electron is remote from material things and devoid of electric and magnetic fields, the net force acting on it will be zero.