This activity will help students understand that gravity is affected by the magnitude or size of the gravitational force between two objects and the masses and distance between them.
Invitation to Learn
Gravity is affected by the magnitude or size of the gravitational force between two objects. It also depends on the masses and distance between them. A larger mass means a stronger gravity, and a shorter distance between objects also means stronger gravity. Gravity accelerates all objects at a constant rate. For example if a penny and a piano were dropped from a tall building at the same time, ignoring friction from the air, they would fall to earth at the same time.
A few days before the activity, you want to ask the students to bring in a Matchbox car. Some students will bring them in but have some extras available for those students who do not have them.
1. Use Science Process and Thinking skills
2. Manifest Scientific Attitudes and Interests
3. Understand Science Concepts and Principles
4. Communicate Effectively Using Science Language and Reasoning
Invitation to Learn
Ask students to find a place in the classroom where they can stand with their backs up against a wall. If it is problem in your classroom, take them in the hall or somewhere where they can do this activity. Make sure each students have their heels back against the wall. Next set a plastic cup about 20 cm from one of the students' feet. Then ask the student to pick up the cup without bending their knees. Before they perform this activity have them predict, in their journals or orally, what they think will happen. Will they be able to pick up the cup? It is impossible to do. They almost want to fall over. Then have the students move away from the wall about a foot or so and try it again. This time the students should be able to pick up the cup without bending their knees. They can do this because as they push with their backsides away from the wall it keeps their center of gravity right in the center of their bodies.
After this activity ask the students what was happening. Have them answer this question in their science journals or orally.
Responses should be close to or equal to these: the more I lean the more I felt I was going to fall over. I couldn't bend because I was too close to the wall. When I was away from the wall I picked up the cup easily. Have them share their responses with the whole class.
Background info for teacher: The reason this activity works is because the body's center of gravity.
This all has to do with the center of gravity. In order for us to pick something up, the legs and lower body have to move backwards. In order to stay balanced, the center of gravity of our body has to remain above our feet which is the pivot point supporting our body. So staying straight with your back against the wall made it impossible for you to move your lower part of your body backward, forward bending of the upper body shifts the body center of gravity toward the front of the pivot point and the whole body topples or moves forward.
Or in technical terms: center of gravity is the point where an object balances and where all the weight of an object appears to be located.
This activity needs to be done in an area where the cars can move forward freely, such as a gym, a hall or outside as long as the area is flat without any obstacles in the way. A classroom would probably be too small; you want the cars to move freely. Each team will have one car. You can choose how you want to make your groups.
Make a large table like the one shown below on the board or chart, have each team report their median distance for each weight. Record their results on the table.
|Team Number||No Washers||1 Washer||2 Washers||3 Washers|
Tobin, K. (1987) The role of wait time in higher cognitive level learning, review of educational research. JSTOR
Wait time is the duration of pauses separating utterances during oral interaction with the teacher and students. This article states the importance of the wait time. When wait time is greater than three seconds, changes in teacher and student discussions were observed and higher cognitive level achievement was obtained in elementary, middle, and high school science. Wait time appears to facilitate high cognitive level learning by providing teachers and student with additional time to think, thus allowing students to cognitively think about the processes asked of them by the teacher.
Huary, D. (1993). Assessing student performance in science, ERIC source. Retrieved January 27, 2007, from http://www.stemworks.org/digests/dse93-8.html
The article discusses how assessment is changing in science education. Assessment in this context must be inconspicuous. It needs to be tailored to measure specific learning outcomes. Assessment is more than testing, multiple choice, short answer, etc., it includes such techniques as systematic teacher observation and so-called "authentic" assessment, in which the tasks assessed more closely parallel the learning activities and outcomes that are desirable in the science classroom (Kober, 1993). Assessment should be context dependent; reflect the nature of the subject matter; and address the unique cultural aspects of class, school, and community among culturally diverse populations (Tippins & Dana, 1992). The article talks about the new assessment that many teachers are using. Among the most promising techniques is the use of scoring rubrics, and students knowing how to achieve the highest level of mastery. Another new assessment is the use of portfolios; these assemble evidence of skill attainment. Some other assessment tools are concept mapping, journal writing (techniques are used to document conceptual change among students), and student presentation and interview techniques (which allow learners to communicate their understanding in ways that rely less on reading and writing skills).