Lesson 7 of 15
Objective: SWBAT develop an understanding of the gravity concept.
Setting the Stage
*Science Notebook, *tennis balls, *basketballs, *ladder, *digital timer
Today's class will start in with the students gathering in a circle with their science notebooks. I will show them a video of an astronaut walking on the moon. This will serve as a hook and a entry point into a discussion about gravity. The class will then be asked what object do they think would hit the floor first (if dropped from the same height) a basketball or a tennis ball? Students will make predictions about the result. As a class we will create a plan, create table to record results and then discuss the results. The lesson will end with the students answering the question, Do objects fall at the same speed?
NOTE: Our district in transitioning to the NGSS. Although we are implementing some of the units this year, I am still required to teach units that have now been assigned to other grade levels. This unit is one of those units that has been affected by the shifts in grade levels. I continue to teach this unit because it focuses on the National Science Standard (K-4) B. "As students describe and manipulate objects by pushing or pulling, throwing, dropping, and rolling, they also begin to focus on the the position and movement of objects."
It is also important that students learn that pushes and pulls can have different strengths and directions, and can change the speed or direction of its motion to start or sot it. It is important that students understand that "the position and motion of an object can be changed by pushing or pulling. In this case gravity is the force that is pulling on the object. The size of the change is related to the strength of the push or pull." Establishing this knowledge base will prepare them for 3rd grade when the NGSS requires them to apply concepts of force and motion into their learning (3-PS2).
"We have an exciting science class today. We are going to start by following astronauts into space and landing on the moon. I would like everyone to slide in front of the Smart Board. I am going to show you a video of the first astronauts to land on the moon. I want you to watch what happens as they start walking around on the moon. Their steps will look a little different than if they were just walking around our classroom."
I am showing the students this video to capture them with a quick trip to space. I want to see if they (through a whole group discussion) can come up with the concept of gravity on their own. If it does't happen, I will guide the discussion toward that focus.
"Why were the astronauts bouncing? Why don't we bounce when we walk around the room?"
I have included a video, Gravity on the Moon, that captures this discussion.
I am choosing to keep this as a whole group discussion because I feel it will be a challenge for some of the kids to understand and they will be better served by hearing ideas from the group as a whole.
"We are going to work on an exploration as a whole class today. As we have discussed (in previous lessons) objects will move when a force is applied to them. Today we are going to see what happens when two balls are dropped from the same height. Let's look at the first ball. It is a tennis ball. What will happen if I let this fall out of my hand? Why will it fall to the floor?"
"The second ball is a basketball. What will happen if I drop this one?"
I want to see if they can connect the idea of gravity (discussed in the first section) to why the balls will fall to the floor.
"We are going to try a whole class investigation today. If I was to drop each of these balls from a really tall ladder, would they hit they the floor at the same time? Before we start I would like each of you to make a prediction in your science notebook. Who can tell me what a prediction is?"
I foster a brief conversation about this but don't want to spend too much time. I spend the whole year focusing on different parts of the scientific process and the students will have plenty of opportunities to gain a more solid understanding of predictions.
"I would like you to open up your science notebook and label the corner with the date and today's focus (falling balls). Now I want you to write the words "I predict" and then write what you think will happen. Will the balls hit the floor at the same time?"
"We are now going to go to the gym. We will conduct a test where we drop each ball from the top of a ladder. We will use timer to keep track of how long it takes each ball to fall and we will test each ball three times. I am going to hand each of you a Table to record your times on. Scientist use tables to display their data in an organized way. I know you have seen tables in math class and this table will function in the same way."
I am choosing to give a pre made table. At this put in the year, I want the students to focus on adding data and not spending the time creating the actual table.
I explain the drops to the students and model what it will look like (Explaining the Drop).
I conduct the investigation with the class and and have a student/or another adult help with the timing. As I am dropping the balls and between each drop, I am talking about the importance of starting and stopping the timer at precise moments and also about dropping each ball front he exact same spot each time. I use this conversation to talk about the term variables and why the variables have to stay the same each time. I will round each time to the nearest second to make it easier to interpret the data and to eliminate split second delays in starting or stopping the clock. After each drop, we fill in the table as a class.
After the test, we head back to the classroom.
"I would like you to bring for notebooks to the carpet area and form a circle for our science circle discussion."
"You all made a prediction today about the balls and wether or not they would hit the floor at the same time. Based on our data, what can you say about your prediction?"
I ask for students to share their results compared to their predictions and then move onto the final question.
"I now want you to think about this final question. Do objects fall at the same speed? Using your data how can you prove that your answer to this question is correct?"
I am teaching students to use data to form a reasonable answer. I am getting them to answer based on fact rather than opinion.
To finish the lesson, I come back to the original discussion about gravity being a force and how it relates to the balls falling at the same speed.
"We know gravity is a force and it is a force that pulls things toward the floor. The force is always there and always has the same strength. That being said, does it make sense that the balls fell to the floor at the same speed? Why?"
"I would like you to draw a picture of what you learned from today's experiment and how gravity affected the balls falling to the floor."
There is no formal evaluation of this lesson. I look at each students notebook to see how they described their learning from today and if they are able to represent gravity effect of pulling the balls to the floor.