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

Forces and 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)

    Source - Practical physics/ Force and motion/ Components of motion

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

    View Resource
  • Episode 207: Projectile motion (16-19)

    Source - TAP/ Mechanics/ Kinematics

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


    View Resource


The following studies have documented this misconception:

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


    Review sheet

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


    This study analysed a sample of 82 high school students (36 boys and 46 girls) between the ages of 16 and 17 using a qualitative multiple choice test on projectile motion. The test was administered both prior to and after a 4-week instructional period. The study took place in the department of physics at Ataturk University, Erzurum, Turkey.
    Review sheet

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