Forces and motion : D-T and V-T graphs

Distance time graphs 

Velocity Time graph

Velocity is speed in   direction e.g 30 mph north or 20 m/s,060 degreesparticular

A force is simply a push or a pull. 

Gravity or Weight always acting straight downwards. Reaction Force from a surface, usually acting straight upwards Electrostatic Force between two charged objects. The direction depends on the type of the charge (like charges repel, opposite charges attract) Thrust or Push or Pull due to an engine or rocket Speeding something up. Drag or air resistance or Friction which is slowing the thing down  Lift due to an aeroplane wing  Tension in a rope or cable 

Reaction  

Thrust

Weight

Drag 

An object with a weight feels a reaction force back from the surface it's on. Otherwise it would just keep falling.

When an object moves in a fluid  (air, water .etc.) it feels drag in the opposite direction to its motion. 

Friction is always there to slow things down

1) If an object has no force propelling it along, it will always slow down and stop because of friction (unless you're out in space where there's no friction). Friction is a force that opposes motion.2) To travel at a steady speed, things always need a driving force to counteract the friction.3)Friction occurs in three main ways:a) Friction between solid surfaces which are gripping (static friction)b)Friction between solid surfaces which are sliding past each other.You can reduce both these types of friction by putting a lubricant like oil or grease between the surfaces. Friction between solids can often cause wear of the two surfaces in contact.c)Resistance or Drag from fluids (liquids or Gases, e.g Air The most important factor by far in reducing drag in fluids is keeping the shape of the object streamlined, like sports cars or boat hulls. Lorries and caravans have "deflectors" on them to make them more streamlines and reduce drag. Roof boxes on cars spoil the streamlined shape and so slow them down. For a given thrust , the higher the Drag, the lower the top speed of the car.The opposite extreme to a sports car is a parachute which is about as high drag as you can get-which is. of course, the whole idea . In a FLUID, FRICTION always INCREASES as the SPEED INCREASES.

Distance Time Graphs

Velocity Time graph

Forces

Friction