Horizontal Launch Lab

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Objective

Students will be able to predict the distance a horizontally launched projectile travels before hitting the ground.

Big Idea

Students roll marbles down ramps and try to hit a target.

Context & Equipment Needs

During the previous lesson students learned the fundamentals of horizontal launches (HS-PS2-1), so today the goal is to apply that knowledge. The lesson starts with a 1-minute essay before students launch into the activity (SP3 & SP5).  As closure, students connect the 1-minute essays created at the start of class to the lab activity in a starring activity. 

This lab requires students to build a ramp, so I use meter sticks held together with masking tape or boards from an old bookshelf. My students choose how to support the ramp, and usually do so with text books or ring stands. Other materials needed for this lab include (1 per group):  blank 8.5x11" paper, carbon paper, marble, and stopwatch.

Introduction with a 1 Minute Essay

5 minutes

To start class today, students come into the room and take out a blank sheet of notebook paper. On the board I've written "What are the standard assumptions we make for horizontally launched projectiles?"

This is a 1-minute essay technique; students get only 1 minute to answer the question and must work individually. The goal is to get students thinking about what they already know before they even start the lab on projectiles. I use a stopwatch, but because some of my students need a little time to process, I usually give them about 90 seconds.

After their time is complete, I ask for volunteers to share their essays. I try to only be a facilitator during this process and let students consider the responses of their peers. For example, if a student makes an assumption that is not valid, I let another student speak up and question the invalid statement. As they listen, I encourage students to write down any valid ideas that they had forgotten to include. Students keep these mini-essays as a reference for them to use during today's lab.

The student samples from today's essay show me that students have a grasp on the fundamental concepts of horizontal launches. The first student identifies that that velocity remains constant (I wish he would have been specific that it's the horizontal velocity), acceleration works at a rate of 9.8m/s/s in the vertical, and friction is ignored. The second student clearly states that there is no initial velocity in the y-direction and air resistance is ignored. The third sample also references that the initial velocity in the y-direction is zero and acceleration in the vertical is due to gravity. 

Launch Lab Activity

35 minutes

After students have refreshed their minds with the basics of horizontally launched projectiles in the 1-minute essay, it's time to move into the lab activity. I know that my students will not finish the lab in class today, so I allow them to choose partners they feel comfortable meeting outside of class. Groups of three seem to work best for this lab so that there can be a timer, a recorder, and a person in charge of construction and ramp maintenance. After they have chosen their groups, each student needs to come to the front of the room to grab a horizontal launch lab and the necessary materials (see equipment section).

The procedure in the lab document is straight-forward, but I still make sure to circulate throughout the room and check-in with the groups.  I'm offering feedback on their ramp construction and ensuring they are making and recording the proper measurements. I also am their biggest cheerleader when it's time to roll the marble and attempt to hit the target!!

When there is approximately 10 minutes prior to the end of class (5 minutes left of the time I've allowed for this activity), I ask students to put everything back the way they found it and return to their seats.  I also tell them at this point that the lab due date is one week from today.  

This student lab sample is really fantastic and shows me the group understood the purpose and were able to draw some good conclusions.  My only critique of this final document is that the justifications are a bit weak in the conclusion - I would have liked to see direct connections to equations.  The AP Physics 1 exam emphasizes drawing and supporting conclusions with concrete evidence, so it's my goal to get students to practice this justification process in as many formal assessment opportunities as possible.  

Closure with the 1 Minute Essay

5 minutes

To bring the class full circle today, I ask students to take out their 1-minute essays from the first part of class. Students use these last 5 minutes of class to individually look at their assumptions and note where they were used in the lab. I ask students to put a hand-drawn star on the lab document where they applied one of these assumptions. For example, if students wrote down that the vertical acceleration of the marble after it leaves the table is gravity then they should put a star next to part 2, section B.  

When I collect the labs, I can search for evidence that students understood the importance of their assumptions in properly placing the target. This activity (the introduction and closure) helps me to see that not only do students understand the fundamentals of horizontally launch projectiles, but also the application of these concepts into real-world scenarios.