B2
Forces

• Meaning of words
• Force, a primitive concept
• Contact force and non contact force
• Plastic materials and elastic materials
• Contact force: elastic force
• Non contact force: weight
• The effects of forces
• Active forces and passive forces
• How to compare forces
• A property of elastic bodies: from qualitative to quantitative
• Spring scale
• The unit of measurement of forces
• How to use the spring scale
• Vector representation of forces
• The center of gravity
• When a body falls freely
• The weight does not remain constant
• Do heavy bodies or light bodies fall first?
• The origin of weight and the force of gravity
• Why does not the moon fall on the earth?