Many students think the downward motion of a projectile will be affected by its horizontal motion

Students may think that an object projected horizontally will fall less quickly than one that is simply dropped.

Studies claim that this is due to the presence of a moving frame of reference. An object seems to fall straight down/backwards as the carrier also moves forward at a constant speed.

Resource to Address This

• Independence of vertical and horizontal motions (11-16)

  This resource is a simple experiment showing a difficult idea: that the time of fall is unaffected by any horizontal motion.

  View Resource

• Episode 207: Projectile motion (16-19)

  This episode looks at the independence of vertical and horizontal motion. It concerns objects accelerating vertically when projected horizontally or vertically.

  View Resource

References

• Dilber, R., Karaman, I. and Duzgun, B. (2009) High school students' understanding of projectile motion concepts. Educational Research and Evaluation, 15 (3), 203-222.

  Addressing misconceptions students have about motion can be difficult, especially more complex ideas such as projectile motion. This study demonstrates that interventions can be effective if they are designed to challenge misconceptions explicitly. Simulations can be very beneficial in this process as they allow students to more easily visualise forces and discuss how they affect motion.
  
  Paper digest

• McCloskey, M., Washburn, A. and Felch, L. (1983) Intuitive physics: The straight-down belief and its origin. Journal of Experimental Psychology: Learning, Memory, and Cognition, 9 (4), 636.