In this article, a second-order sliding mode control (2-SMC) is proposed for second-order uncertain plants using equivalent control approach to improve performance of control systems. A Proportional+Integral (PI) sliding surface is defined for the sliding mode. The sliding mode control law is derived using direct Lyapunov stability approach and asymptotic stability is proved theoretically. The second-order plant parameters are experimentally determined using input-output measured data. Performance of the closed-loop system is analysed through an experimental application to an electromechanical plant to show feasibility and effectiveness of the proposed 2-SMC and factors involved in the design. Results of the experimental application are presented to make a quantitative comparison with the traditional (first-order) sliding mode control and PID control. It is demonstrated that the proposed 2-SMC system improves performance of the closed-loop system with better tracking specifications in the case of external disturbances, better behavior of the output and faster convergence of the sliding surface while maintaining the stability.