In Module 3 you saw that a non-zero (unbalanced) net force will cause a change in velocity. You examined Newton’s first law of motion to help you understand the forces acting on an object at rest and an object with uniform motion. Newton’s second law of motion helped explain the relationships among net force, mass, and acceleration. You applied Newton’s third law of motion to interactions between two objects and recognized that the two equal and opposite forces act on different bodies. You examined the differences between static and kinetic forces of friction. You were able to apply vector tools from Unit A to calculate the resultant force acting on an object. Finally, you applied Newton’s laws of motion to solve linear-motion problems in horizontal, vertical, and inclined planes near the surface of Earth.
From this, you can see how understanding forces can help humans improve and change our environment. Many improvements in transportation have been brought about through technological advancements that reflect this understanding. Seatbelts, timing of traffic lights, runway design for airplanes, and space travel are only a few areas where the applications of the principles of dynamics have led to improvements and the development of new mechanical technologies.
In Module 4 you saw that the gravitational force is one of the fundamental forces in nature. You examined the principles of the Cavendish experiment and studied Newton’s law of universal gravitation and used it to relate the gravitational constant to the local value of the acceleration due to gravity. You defined field as a concept that replaces action at a distance. Finally, you predicted differences in weights of objects on different planets.
You should now have a clearer picture of gravitational effects in the universe. You can distinguish between mass and weight in space or on Earth. You can see the relationship between acceleration due to gravity and gravitational field strength. The concepts, models, and theories studied in this module are often used to interpret and explain observations and to predict future observations.
The understanding of dynamics and kinematics that you gained in Units A and B will form a strong foundation for the new concepts related to motion you will explore in Unit C.