1. Line Graphs, Elastic Force, and Frictional Force Quiz 2

2. Lesson 3: Elastic Force The two types of elastic force are tension and compression. The elastic force of a rubber band is directly proportional to the stretching distance. – Approximately, the elastic force doubles when the stretching distance doubles. – Therefore, if at 2 cm the elastic force is 1.0 N then at 4 cm you could estimate that the elastic force would be 2.0 N.

3. Elastic Force and Newton’s Third Law of Motion Newton’s Third Law of Motion: For every action, there is an equal and opposite reaction. – The rubber band is an example of Newton’s Third Law of Motion because as the rubber band is stretched (the action), it pulls back on the spring scale creating force (the reaction).

4. Lesson 4: The Force of Friction Static Friction – friction between two objects that are not moving. – Example: When you first try to pull the block across the surface, it seems stuck. This is because of static friction. It takes a certain amount of force to overcome the static friction. Unbalanced Force – When two forces acting on an object are not equal in size. – Unbalanced forces cause a still object to move. a moving object to speed up or slow down, a moving object to stop, a moving object to change direction.

5. Lesson 4: Unbalanced Force An example of an unbalanced force from lesson 4 was the force of your hand pulling the block, which was stronger than the force of friction. The two forces were the force of your hand pulling the block and the force of friction.

6. What causes a change in friction? Changing the Surfaces Changing the type of surface the block is on will change the force of friction. – The tabletop had the least amount of friction and the sandpaper had the most amount of friction. Changing the Surface Area Changing the side of the block in contact with the surface did NOT change the force of friction.

7. Changing the Weight Changing the weight of the block (adding more blocks) did change the force of friction. – The weight of the block is directly proportional to the force of friction. – Doubling the weight (# of blocks), doubles the force of friction.

8. Graphing: Axes The x-axis is on the bottom. The y-axis (y to the sky) is on the side. The independent variable (what you change) goes on the x-axis. The dependent variable (what is determined by the experiment) goes on the y-axis.

9. Graphing: Labeling Each axis must include a label with units of measurement in parentheses. For example, “Stretching Distance” is the label and “(cm)” standing for centimeters are the units of measurement in parentheses. – You could usually find the labels and units of measurement as the data table column labels. At the top of a graph should be a title explaining what is being graphed.

10. Graphing: Uniform Scale Each axis should have a set of numbers starting at 0. Depending on the data, each axis should only go 1 or 2 numbers higher than then highest point. – For example, if the data only goes up to 14 then the axis scale should go up to around 16. Each axis should have the numbers spread out along the axis. Each axis should have a pattern. For example: 0.5, 1.0, 1.5, 2.0, 2.5

11. Graphing: Line A straight line should go through most if not all the points. You should NOT connect the points, but rather draw a straight line through them.

12. Vocabulary to Study Extrapolation Direct Proportion Independent Variable Dependent Variable Friction Static Friction Unbalanced Force