Question

If a constant force acts on a particle, its acceleration will

(a) remain constant
(b) gradually decrease
(c) gradually increase
(d) de undefined

Answer 1

(d) gradually decrease

If a constant force is acting on a particle, the force will tend to accelerate the particle and increase its speed. But, due to increase in speed, the mass of the particle will increase by the relation $m=\frac{m_o}{\sqrt{1-{\displaystyle \frac{v^2}{c^2}}}}$ leading to decrease in acceleration as constant force is acting. Therefore, after sometime its acceleration will start decreasing gradually.