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# 7K Forces ## 1. Different Forces | Force | Description | |---|---| | Force | A push or a pull. The thing providing the force needs to touch an object to affect it. | | Contact Forces | | | Upthrust | The force that makes things float. | | Air Resistance | A force acting on objects moving throug...

# 7K Forces ## 1. Different Forces | Force | Description | |---|---| | Force | A push or a pull. The thing providing the force needs to touch an object to affect it. | | Contact Forces | | | Upthrust | The force that makes things float. | | Air Resistance | A force acting on objects moving through the air. | | Water Resistance | A force acting on objects moving through water. | | Non-Contact Forces | Forces that can affect an object from a distance; Gravity, static electricity, magnetism | | Gravity | A force that pulls objects downwards. | | Static Electricity | A force that attracts things. | | Magnetism | A force that attracts objects made of iron, nickel or cobalt. | **Units:** * Newton (N) - the units for measuring forces. * Weight - The force of gravity pulling on something - measured in Newtons (N). * Mass - The amount of matter that makes up something - measured in kilograms (kg). ## 2. Springs | Description | Details | |---|---| | Stretched Spring | Made longer. | | Compressed Spring | Made shorter. | | Made from coils of wire| | | Extension |difference between the original length and the stretched length. An object that returns to its original length when the force is removed. | | Elastic | An object that return to its original length when the force is removed | | Investigating Extension | Hang a spring from a clamp and measure its length. Add increasing numbers of masses and measure the extension each time. | | Hooke's Law | Extension is proportional to the force applied. A relationship between two variables where if one doubles, the other will double. | | Proportional | A relationship between two variables where when one doubles, the other doubles. | | Limit of Proportionality | The point at which the extension and force are no longer proportional. | | Elastic Limit | The point at which the spring cannot return to its original length. | |Force Meter | Springs are used inside to measure the force. | **Diagram Descriptions:** A force diagram is provided showing a diver in water with arrows indicating upward thrust and forces from water resistance in the opposite direction. Also, there are arrows pointing towards forward from the diver's legs. **Representing Forces:** We draw arrows on force diagrams to show the direction of a force; a bigger arrow shows a bigger force.