1 - FORCES AND MOTION 

Forces and friction - 

• Gravity/weight - straight downwards 
• Reaction force - from surface, usually straight upwards 
• Electrostatic force - between 2 charged objects (direction depends on type of charge, eg: repel, attract etc) 
• Thrust/push/pull - eg: due to engine or rocket speeding something up 
• Drag/air resistance/friction - slowing object down 
• Lift - eg: due to aeroplane wing 
• Tension - eg: in rope or cable

 Friction - 

• Opposes motion (unless in space)
• To stay at a a steady speed, there needs to be a driving force to counteract friction

1. Static friction - between solid surfaces that are gripping 
2. Sliding friction - between solid surfaces that are sliding past eachother (lubricant between surfaces eg: oil/grease) 
3. Resistance/drag - can be reduced by making object streamlined, lowers top speed of an object (eg: parachute)