Force Balance - Introduction to Force & Gravity

Ask questions that arise from careful observation of phenomena, models, or unexpected results, to clarify and/or seek additional information.

Evaluate limitations of a model for a proposed object or tool.

Conduct an investigation and/or evaluate and/or revise the experimental design to produce data to serve as the basis for evidence that meet the goals of the investigation.

Construct, analyze, and/or interpret graphical displays of data and/or large data sets to identify linear and nonlinear relationships.

Use mathematical representations to describe and/or support scientific conclusions and design solutions.

Construct an explanation using models or representations.

Apply scientific ideas or principles to design, construct, and/or test a design of an object, tool, process or system.

Critically read scientific texts adapted for classroom use to determine the central ideas and/or obtain scientific and/or technical information to describe patterns in and/or evidence about the natural and designed world(s).

Communicate scientific and/or technical information (e.g., about a proposed object, tool, process, system) in writing and/or through oral presentations.

Each force acts on one particular object and has both strength and a direction. An object at rest typically has multiple forces acting on it, but they add to give zero net force on the object. Forces that do not sum to zero can cause changes in the object�s speed or direction of motion. (Boundary: Qualitative and conceptual, but not quantitative addition of forces are used at this level.)

The motion of an object is determined by the sum of the forces acting on it; if the total force on the object is not zero, its motion will change. The greater the mass of the object, the greater the force needed to achieve the same change in motion. For any given object, a larger force causes a larger change in motion.

All positions of objects and the directions of forces and motions must be described in an arbitrarily chosen reference frame and arbitrarily chosen units of size. In order to share information with other people, these choices must also be shared.

Objects in contact exert forces on each other.

Gravitational forces are always attractive. There is a gravitational force between any two masses, but it is very small except when one or both of the objects have large mass (e.g., Earth and the Sun).

The faster a given object is moving, the more energy it possesses.

Motion energy is properly called kinetic energy; it is proportional to the mass of the moving object and grows with the square of its speed.

A system of objects may also contain stored (potential) energy, depending on their relative positions.

When the motion energy of an object changes, there is inevitably some other change in energy at the same time.

Models of all kinds are important for testing solutions.

Graphs, charts, and images can be used to identify patterns in data.

Write, read, and evaluate expressions in which letters stand for numbers.

Use variables to represent quantities in a real-world or mathematical problem, and construct simple equations and inequalities to solve problems by reasoning about the quantities.