Projectile Motion and Gravity

Greg Westendorf, Heritage Middle School, West St. Paul, MN, based on a original activity from Holt, Forces and Motion
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In this physics lab student will investigate how gravity affects an object that falls from a resting state and how it affects an object that is projected out from the same resting state. Students will predict which object will hit the ground first if set in motion at the same time.

Learning Goals

Concept: Gravity affects all objects at the same rate.
Students will set 2 objects in motion at the same time. One from a state of rest and a second that is projected outward from the same level at the same time. Student will use observation to determine which will object hits the ground first.

Vocabulary: gravity, acceleration, projectile motion.

Context for Use

This is a mini lab that takes about 5 minutes. Equipment needed are 1 ruler, two flat objects (coins, washers, discs...), Table or desk.

This activity is used after discussing the concept of gravity and acceleration. This activity is very straight forward and does not need to be adapted.

Description and Teaching Materials

Place a ruler on a desk with one edge hanging 3- 4 inches over the edge desk.

Place one object on the ruler and the other next to the ruler and the edge of the table.

Quickly move the ruler to strike the object on the desk.

Have students listen/watch both objects to determine which object hits the floor first.

Prior to conducting the activity have students predict which object will hit the floor first.

This activity can be done as a class demonstration or in small groups. Projectile Motion image

Teaching Notes and Tips

Space is needed to conduct this activity. Larger objects are easier to see. Also if you conduct this activity on a tile floor students can hear the object fall and determine which object hits the floor first


Students should see and understand that both objects hit the ground at the same time. Students summarize their results by making a poster of writing a paragraph to show understanding


Motion: Recognize that when the force acting on an object are balanced, the object remains at rest or continues to move at a constant speed in a straight line, and that unbalanced forces cause a change in speed or direction of the motion of the object.

Motion: Recognize that some forces between objects act when the objects are in direct contact and others, such as magnetic, electrical and gravitational forces can act from a distance.

References and Resources