Force affects our daily life in many ways. Force can change the motion of an object but it is not required in maintaining a motion. An object will stay at rest or in uniform motion when the forces acting on it are balanced. Gravity and friction are examples of forces and their effects on motion are commonly found in everyday experience. Forces are always working in action and reaction pairs. When an object is being pushed, the object pushes back with a force of equal magnitude and in an opposite direction. The scenario of space flight provides an interesting context for us to appreciate how the understanding of forces and motion is put into application.

This Unit introduces the basic concepts about force and motion. Through drawing distance-time graph and performing practical work to observe the phenomena of action and reaction, students develop some science process skills such as observing, inferring and communicating using graphical representation. The design and make activities provide opportunities to foster students’ creativity and innovation, and develop their abilities to integrate and apply knowledge and skills of science and other disciplines. Through learning about the effects of forces on the motion of an object, students will recognise the unifying concepts “change and constancy”.