Mobile phone technology has been developed tremendously in the last two decades. The smartphone's emergence has shifted the primary function of a mobile phone because it provides various advanced features. Multiple features in the smartphone are the potential to be utilized in education. In this paper, we report a study that aims to develop a Straight Motion application, a mobile application designed as a learning resource on linear motion topics. The application is targeted to high school students as a resource for prelecture preparation or post-lecture review and individual study. Straight Motion application is evaluated by an expert in physics and physics education. According to the evaluation, the application is feasible to be used by high school students in learning physics. We also conduct field testing, which involves 63-grade 10 th students. To investigate the learning improvement, we give pre-and post-test to students before and after they use Straight Motion for learning linear motion. The calculated normalized gain is 0.56, which can be classified as medium gain. Moreover, students also give an excellent response to the use of Straight Motion in the learning process.