## Getting Started

A comprehensive course that continues the science adventure in physics under Newton’s work on the three laws of motion.

(Note: If you’re wanting a more in-depth physics course (not just lab experiments but additional content including calculations), then you’ll want to visit our Physics Course in the Advanced section. You do not need to complete the content on this page in order to do the Advanced Physics Course.)

Students get a crash-course in projectile motion as they build g-force accelerometers, float hovercraft on both land and water, build a rocket car, and measure the Earth’s magnetic pulse. For advanced students, you’ll find a complete course in thermal energy here to augment the topics covered in this section.

## Here are the scientific concepts:

• The velocity of an object is the rate of change of its position.
• To describe the velocity of an object one must specify both direction and speed.
• Changes in velocity can be changes in speed, direction, or both.
• Position is defined relative to some choice of standard reference point and a set of reference directions.
• Average speed is the total distance traveled divided by the total time elapsed. The speed of an object along the path traveled can vary.
• A force has both direction and magnitude.
• When an object is subject to two or more forces at once, the effect is the cumulative effect of all the forces.
• When the forces on an object are balanced, the motion of the object does not change.
• How to identify separately two or more forces acting on a single static object, including gravity, elastic forces due to tension or compression in matter, and friction.
• The greater the mass of an object the more force is needed to achieve the same change in motion.
• 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 (Newton’s third law).
• 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.
• Electric and magnetic (electromagnetic) forces can be attractive or repulsive, and their sizes depend on the magnitudes of the charges, currents, or magnetic strengths involved and on the distances between the interacting objects.
• 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.
• Forces that act at a distance (electric and magnetic) can be explained by fields that extend through space and can be mapped by their effect on a test object (a ball, a charged object, or a magnet, respectively).
• Motion energy is called kinetic energy, and is proportional to the mass of the moving object and grows with the square of the speed.
• A system of objects may also contain stored (potential) energy depending on its location.
• When two objects interact, each exerts a force on the other that can cause energy to be transferred between the objects.

## By the end of the labs in this unit, students will be able to:

• Construct and interpret graphical displays of data to describe the relationships of kinetic energy to the mass of an object and to the speed of an object.
• Design an experiment that shows when the arrangements of objects interacting at a distance changes, different amounts of potential energy are stored in the system.
• Show that when the motion energy of an object changes, energy is transferred to or from the object.
• How to solve problems involving distance, time, and average speed.
• How to interpret graphs of position versus time and speed versus time for motion in a single direction.
• Apply Newton’s Third Law to design an experiment involving the motion of two colliding objects.
• Design and build an experiment that shows how the change in an object’s motion depends on the sum of the forces on the object and the mass of the object.
• Determine the factors that affect the strength of electric and magnetic forces.
• Show that gravitational interactions are attractive and depend on the masses of the objects.
• Design and build an experiment that shows that fields exist between two objects that are not touching.
• Differentiate observation from inference (interpretation) and know scientists’ explanations come partly from what they observe and partly from how they interpret their observations.
• Measure and estimate the length and volume of objects.
• Formulate and justify predictions based on cause-and-effect relationships.
• Conduct multiple trials to test a prediction and draw conclusions about the relationships between predictions and results.
• Construct and interpret graphs from measurements.
• Follow a set of written instructions for a scientific investigation.