Our students have studied Motion in previous grades and we wanted to ramp up our Forces and Motion unit this year. To introduce the unit, we went on a Motion Hunt around our school. We made a T-Chart of things we use push and pull to move. Obviously, 3rd graders know what push and pull are and we want to challenge them in their understanding of science.
Next, we discussed Isaac Newton's 3 Laws of Motion. I used George Power's FREEBIE TpT ppt to help explain the Laws. We went through example of each Law.
Second Law of Motion: Mass x Acceleration = Force Basically, it takes more speed to move objects with more mass and less speed to move objects with less mass. For example, if you throw a bowling ball and a basketball (roughly the same size), the basketball will go farther because there is less mass weighing it down.
Third Law of Motion: For every action, there is an equal and opposite reaction. When I sit in a chair, my force is pushing down on the seat (action) and the seat is pushing up on me (opposite action). For me to rest on the chair, those forces must be equal. If my force was greater than the chair's, it would break and I would fall. If the chair's force was greater than mine, I would float off the chair. One of my students asked about a beanbag chair, and I thought that was a great example of a chair with less force (since you sink into the chair as you sit).