Lesson Plan Industry Sector
Engineering & Design

## It Really is Rocket Science Part 2

### Lesson Plan Overview / Details

Students continue to explore the concept of gravity by experimenting with air resistance. Galileo's famous, if only apocryphal, experiment at the Tower of Pisa is reviewed, discussed, and replicated. A parachute provides outdoor learning opportunities, and students culminate this lesson with an egg drop activity.

approximately
100 Minutes

### Objectives and Goals

• Students will experiment to discover the effect of gravity and air resistance on the motion of falling bodies by dropping various objects from a second story balcony.
• Students will apply Newton's three Laws of Motion by making a parachute and explaining how it works in terms of forces.
• Students will demonstrate and apply knowledge of gravity and air resistance by making an egg drop device and dropping it from a second story balcony.

### Activities in this Lesson

• Aristotle vs. Galileo - Hooks / Set

Get two of the same water bottles, but empty one of them. As students enter, ask them to examine the two bottles.

When students are seated, ask them what will happen if you drop the bottles (they will fall). Ask them what is the force that makes them fall (gravity).

Tell the students that you are going to drop the two bottles at the same time. Ask who thinks that the empty bottle will hit the ground first. If any one thinks that, ask them to explain why. Then have them re-think that answer. Next, ask who thinks the full bottle will hit first. Ask someone to explain why. Tell them they are Team Aristotle. Then, ask who thinks they will hit at the same time. Tell them they are Team Galileo and it is time for a contest.

You could just climb up on a desk and drop the bottles, but it is more exciting if you can find a second floor balcony to do the drop. If you do it right, Team Galileo will win.

See below for a link to a fun interactive Galileo game; you have to guess what happens when two balls are dropped out of a window.

• Galileo Game http://www.pbs.org/wgbh/nova/pisa/galileo.html
• Galileo Galilei was an Italian scientist from the late 1500's and early 1600's. He is most famous for improving the telescope and using it to observe the planets. His observations led him to believe that the planets revolved around the Sun, as first hypothesized by Nicolaus Copernicus. This got him in trouble with the Catholic Church, which supported Aristotle's theory that the Sun and the planets revolved around the Earth. Aristotle was a Greek philosopher from the 300's BC. He thought that objects that weigh more fall faster than objects that are lighter weight.

But Galileo was also a mathematician, and he used math to explain science. He used math, logic, common sense, and everyday experiences to explain how forces work. He described how an object resists a change in  motion; we call this the Law of Inertia. Isaac Newton used this idea to form his First Law of Motion. Galileo died in 1642, the same year thet Newton was born.

See below for links to two short videos on Galileo's Tower of Pisa experiment. Legend has it that Galileo challenged the generally accepted theory of Aristotle that heavier objects fall faster. So he climbed up the Tower of Pisa and dropped two balls at the same time, one made of lead and one made of wood. Even though it is a famous story, Galileo himself probably did not actually drop the two balls from the Tower.

• Galileo Experiment Video 4 minutes http://www.youtube.com/watch?v=_Kv-U5tjNCY&NR=1
• Galileo Animation 30 seconds http://space.about.com/library/weekly/blvidgalileopisa.htm
• Air Resistance - Demo / Modeling

When the only force acting on an object is gravity, it will be in free fall. The object will fall faster and faster; this is called acceleration due to gravity. Near the surface of the Earth, this acceleration is about 9.8 m/s 2. All objects in free fall accelerate at the same rate, no matter how heavy they are.

But gravity is not the only force acting on objects we drop. Objects falling through the air have air resistance. Remember that this is a kind of fluid friction, and it acts in the direction opposite to motion. What is this called in an airplane? (drag)

Take two sheets of paper. Now wad one of them up into a little ball. Drop them both at the same time. Which one hit the ground first? (the balled up one) Did it matter that the two papers weighed the same? What if the wadded up paper was only a half sheet? (it would still hit first) Why does the wadded up one always hit first?

Falling objects with a greater surface area have more air resistance. This is the key to how a parachute works.

Air is a collection of gas molecules that have to be pushed out of the way for any object to move through it. These molecules exert force on objects that try to push them out of the way. This is an example of Newton's 3rd Law (for every action there is an equal and opposite reaction).  When the parachute falls through the air, the molecules don't want to move so they push back, slowing the parachute. The parachute experiences air resistance. That resistance is a result of air molecules resisting a change in motion and exerting an opposing force.

• Have students work alone or in pairs. Give each student or pair of students a small plastic trash bag. Try to get your custodian to give you some for free. You could also use plastic grocery bags. I've even used kittly litter box liners. Have students share some scissors. Have students make a parachute from the plastic.

Supply masking tape to use for parachute cords, or use string or yarn if you have some. See who can float a pencil the longest time.

If you can get a real parachute, take the kids outside to play with it. Have them hold the edge and make waves by lifting their arms up and down. Play peek-a-boo by lifting the parachute high, looking at the students standing opposite, and letting the parachute drift slowly down. Play hideaway by lifting the parachute high, everybody steps inward under the parachute, bring the edge down behind you, and sit down on the edge.

You can buy a big twenty foot parachute canopy for about 100 dollars. Army surplus stores might have used ones cheaper. Elementary schools used to use them for Physical Education, so work with your PE department to see if they can find one somewhere in your district that you could borrow.

• Egg Drop - Projects

Culminate the parachute activity with an Egg Drop competition. To make things fair, I measure out the materials I give them, such as one plastic bag, one egg, ten plastic drinking straws, and only two meters of masking tape.

Allow about 30 minutes for them to create their Egg Drop device.  If you spent a lot of time with parachutes and the other previous activities and now you are out of time, just have them sketch a possible design for their Egg Drop to be built the following class meeting.

Once their Egg Drops are complete, have the kids go to the second floor balcony. Prep the landing area by spreading newspaper, flattened cardboard boxes, or an old plastic tablecloth. Have the first student or student pair hold their Egg Drop out over the edge of the balcony and release it; do not have them throw it. This way the only two forces at work are gravity and air resistance. When the Egg Drop lands, check the egg for breakage. Have a large trashcan handy for broken, leaking Egg Drops. Once the first student or students drop it, have them come downstairs and join you at the landing area. Then they will judge the next Egg Drop. If time allows and a higher level is available, you could have a Round Two competition for the survivng Egg Drops.

• Let students decide who won the Egg Drop. They can evaluate the Egg Drops for creativity, craftsmanship, and best parachute. When it's time to go, tell them no one leaves until all the mess is cleaned up.

### Assessment

Assessment Types:
Writing Samples,

Have students explain the forces at work on the Egg Drop and on the parachute.