Science Knowledge Organiser – Summer half term 1: Forces. Key concepts Know the facts- Forces 1 Air resistance A force of friction produced when an object moves through the air. 2 Balanced force When the total force in opposite directions are equal in scale. 3 Contact force Contact forces are forces that act between two objects that are physically touching each other 4 Non-contact force Non-contact forces are forces that act between two objects that are not physically touching each other. E.g. Magnetic force 5 Deformation Changing shape and/or size as a result of forces being applied. 6 Density Density is a measurement that compares the amount of matter an object has in a given volume 7 Effort Force used to move a load over a distance. 8 Elastic Elastic materials return to their original shape and size after being stretched or squashed. 9 Extension Increase in length, for example, as a result of being pulled. 10 Force A push or a pull. The unit of force is the newton (N). 11 Friction Force that resists one object moving through or over something. 12 Hooke's law   The extension of an object or material is directly proportional to the force applied. 13 Load Force in a machine due to the mass, weight or movement of an object. 14 Mass Mass is a measure of the amount of matter in an object. It is usually measured in g or kg 15 Moment A turning effect of a force. Moment = Force x distance from pivot. 16 Newton Unit of force named after British scientist Isaac Newton (1642-1727), e.g. the frictional force on the boat is 20,000 N. 17 Newton's laws If the forces add to zero there is no acceleration. If the forces do not add to zero there is acceleration. All forces come in pairs. 18 Action and reaction forces Action force is force acting in one direction. Reaction force is force acting in the opposite direction. 19 Resultant force The single force that could replace all the forces acting on an object, found by adding these together. If all the forces are balanced, the resultant force is zero. 20 Thrust The force that pushes an object forward. Know the facts- Forces 21 Upthrust The force that pushes an object upwards in a liquid or a gas, also called buoyancy 22 Weight   The force acting on an object due to the pull of gravity from a massive object like a planet. The force acts towards the centre of the planet and is measured in Newtons (N). Know the facts- drawing force diagrams 1 The Object The object can be drawn as a dot 2 The arrows The arrows must be touching the object 3 The size of arrows The size of the arrows represent the size of the force. Larger arrow = larger force Smaller arrow = smaller force A force diagram for a car: this car will move to the right Reaction force Air resistance Engine force Gravity Know the facts- Speed 1 Speed The distance travelled in a fixed time period, usually one second 2 Acceleration The rate of change in speed (or velocity) is measured in metres per second squared 3 Deceleration Slowing down or negative acceleration 4 Distance-time graphs A graph with distance travelled plotted on the vertical axis against time taken on the horizontal axis. Know the facts- Electromagnetism 1 Magnetic Able to be magnetised or attracted to a magnet 2 Magnetic field Area surrounding a magnet that can exert a force on magnetic materials. 3 Electromagnet A magnet made by wrapping a coil of wire around an iron bar and passing an electric current through the coil.