Physics Unit 1

Unit Overview – Force and Motion

The big picture stuff:

Students have been exploring push/pull relationships, throughout their K-8 years, but in high school, students begin using the language of mathematics as evidence from experimentation to support concepts that have been developing for some time. Students go beyond, “will this keep moving” or “will this collide” to “why does this object keep moving and when will it stop?” Understanding Newton’s 3rd law, as relating forces to the motion of objects, helps students frame why some objects move and others don’t in given situations. The NGSS asks students to compare movement of objects as related to gravitational pull to magnetic and electrical forces. The exploration of electromagnetism will occur in a different unit.

Next Generation Science Standards – High School (NGSS-HS):

PS2-1. Apply Newton’s Third Law to design a solution to a problem involving the motion of two colliding objects.

Core ideas: For any pair of interacting objects, the force exerted by the first object on the second object is equal in strength to the force that the second object exerts on the first, but in the opposite direction.

Examples: the impact of collisions between two cars, between a car and stationary objects, and between a meteor and a space vehicle; limited to vertical or horizontal interactions in one dimension

PS2-2. Plan an investigation to provide evidence that the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.

Core ideas: 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 artibrarily chosen reference frame and arbitrarily chosen units of size.

Emphasize: balanced (Newton’s First Law) and unbalanced forces in a system, qualitative comparisons of forces, mass and changes in motion (Newton’s Second Law), frame of reference, and specification of units. Focus on forces and changes in motion in one-dimension in an inertial reference frame, and to change in one variable at a time.

PS2-4. Construct and present arguments using evidence to support the claim that gravitational interactions are attractive and depend on the masses of interacting objects.

Core Ideas: 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)

Examples: data generated from simulations or digital tools; and charts displaying mass, strength of interaction, distance from the Sun, and orbital periods of objects within the solar system.

Science and Engineering:

• Plan an investigation individually and collaboratively, and in the design: identify independent and dependent variables and controls, what tools are needed to do the gathering, how measurements will be recorded, and how many data are needed to support a claim.
• Apply scientific ideas or principles to design an object, tool, process or system.
• Construct and present oral and written arguments supported by empirical evidence and scientific reasoning to support or refute an explanation or a model for a phenomenon or a solution to a problem.
• Scientific knowledge is based upon logical and conceptual connections between evidence and explanations.

Crosscutting Concepts:

• Cause and effect relationships may be used to predict phenomena in nature or designed stems.
• Models can be used to represent systems and their interactions – such as inputs, processes and outputs – and energy and matter flows within systems
• Explanations of stability and change in natural or designed systems can be constructed by examining the changes over time and forces at different scales.
• The uses of technologies and any limitations on their use are driven by individual or societal needs, desires, and values; by the findings of scientific research; and by differences in such factors as climate, natural resources, and economic conditions.

California Science Standards - Physics:

1a. Students know how to solve problems that involve constant speed and average speed.

1b. Students know that when forces are balanced, no acceleration occurs: thus an object continues to move at constant speed or stays at rest.

1c. Students know how to apply the law F=ma to solve one dimensional motion problems that involve constant forces.

1d. Students know that when one object exerts a force on a second object, the second object will always exert a force of equal magnitude and in the opposite direction.

1e. Students know the relationship between the universal law of gravitation and the effect of gravity on an object at the surface of the Earth

Investigation and Experimentation Standards:

a. Select and use appropriate tools and technology (such as computer-linked probes, spreadsheets, and graphing calculators) to perform tests, collect data, analyze relationships, and display data.

b. Identify and communicate sources of unavoidable experimental error.

c. Identify possible reasons for inconsistent results, such as sources of error or uncontrolled conditions.

d. Formulate explanations by using logic and evidence.

j. Recognize the issues of statistical variability and the need for controlled tests.