Practical activities designed for use in the classroom with 11- to 19-year-olds.
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# Testing projectile motion with a drawn parabola

##### Demonstration

This is a demonstration which shows that motion can be predicted.

Object, small

#### Procedure

a Draw a rough parabola by sketching vertical and horizontal lines on a blackboard or whiteboard (see diagram).

b Throw a small object in a vertical plane parallel to the blackboard and near it, so that it follows the curve. With the proper start, the object follows surprisingly well. It is better to start with a parabola which results from throwing the object horizontally.

#### Teaching notes

1 After trying horizontal projection, you could be more adventurous and try the more elaborate path of a complete parabola (see below). Give the object an initial velocity which has both horizontal and vertical components.

2 Discuss how you managed to draw such a perfect parabola, using the idea that the resulting motion for the horizontal (x=vt) and vertical (yat2) components of the motion is a parabola.

3 Their velocity at each instant is a tangent to the parabolic path. The components of a velocity add as vectors.

4 A related experiment shows that the horizontal and vertical motions of a projectile are independent of each other: a video of Monkey and Hunter is freely available from the National STEM Centre eLibrary.

This experiment was safety-checked in March 2005.

#### Related experiments

Page last updated on 09 November 2011