Grade Level: 9th -11th; Type: Physical Science
To find out if falling objects dropped from a higher distance will hit a greater impact force than the same object dropped from a lower distance.
- Why will throwing the ball down rather than dropping it alter the results of the experiment?
- How do we know gravity is always 9.8 m/s²? What exactly is this?
Galileo Galilei was an Italian physicist, mathematician, astronomer and philosopher who played a promiment role in the Scientific Revolution. He supposedly dropped things from the leaning tower of Pisa in order to prove that all objects fall at the same rate, whatever their mass. We'll perform a similar experiment, and try to measure how height affects the force of impact.
- Small, hard ball (like a golf ball)
- Large clear box to hold sand inside
- High building with windows on one side or a ladder (please be careful)
- Ruler and meterstick
- Friend to help you
- Pen and paper for notes
- On the scale, weigh how heavy your ball is (convert to kilograms) and note this.
- Measure the distance from where you are going to drop the ball (in meters) and the surface of the sand. Start at a lower distance. Note this distance.
- Simply drop the ball from above, straight into the sand. Do not apply any force, which means...do not throw it into the sand.
- Carefully take the ball out of the sand and measure the depth of the hole it made, if any.
- Now repeat steps 2-4, but at higher distances. Remember to just drop the ball rather than throw the ball down..as doing that will alter your results.
Now we are going to calculate to find out the impact force of the drop for all the heights. Remember that gravity is always 9.8 m/s² (meters per second squared). We are going to calculate impact velocity with this formula:
- v = √2gh (square root)
- g= gravity
- h= height of the drop (which you should have recorded)
This will give us the impact velocity just before impact.
To calculate kinetic energy (in joules) we will need to use the formula: KE= ½ mv²
- m= mass of object in kilograms
- v= velocity
To find average impact force (in Newtons) using the work-energy principle:
d= distance after collision (which you should have measured in the sand)
So which had a greater average impact force?
Distance After Impact
Distance= ____________ m
Terms/Concepts: Falling bodies/objects; Kinetic energy; Potential energy; Impact; Newtons and joules; Work-energy principle
- From Falling Bodies to Radio Waves (1984) by Emilio Segre. W H Freeman & Co.