distance, displacement, speed and velocity

• difference between distance and displacement

  - distance is a scalar quantity that refers to "how much ground an object has covered" during its motion- displacement is a vector quantity that refers to "how far out of place an object is"; it is the object's overall change in position
• difference between speed and velocity

  - speed is how fast you're going with no regard to the direction (e.g. 20m/s)- velocity is speed in a given direction (e.g. 20m/s 060°)
• why can you have objects travelling at a constant speed but with changing velocity?

  as the direction of motion changes, velocity also changes
• distance (m) =


  speed (m/s) x time (s)
• distance formula

  s=vt
• distance formula triangle

  
• speed of a person walking

  1.5 m/s
• speed of a person running

  3 m/s (depends on fitness, age, terrain, distance travelled etc)
• speed of a cycling

  6 m/s
• speed of a car

  25 m/s
• speed of a train

  55 m/s
• speed of a plane

  250 m/s
• speed of sound

  343 m/s in air(depends on density, pressure, temperature and elasticity of medium)
• wind speed can be affected by...

  temperature, atmospheric pressure, structures nearby
• acceleration

  rate of change of velocity
• acceleration (m/s²) =

  change in velocity (m/s) / time taken (s)
• acceleration formula

  a=Δv/t
• acceleration formula triangle

  
• deceleration

  negative acceleration
• uniform acceleration means...

  constant acceleration
• acceleration due to gravity is ...for objects in free fall - it's roughly 9.8 m/s²

  uniform
• uniform acceleration =

  final velocity (m/s) - initial velocity (m/s) = 2 (acceleration (m/s²) x distance (m)0
• uniform acceleration formula

  v²-u²=2as
• distance-time graph

  line graph used to show the speed of a moving object
• distance-time graph example

  time is on the x axis, distance is on the y axis

  
• the shape of a distance-time graphs shows...

  how the object is moving

  - gradient = speed

  - flat line = stationary

  - straight uphill line = steady speed

  - curved lines = acceleration/deceleration

  - steepening curve = object is speeding up

  - levelling off curve = object is slowing down
• the steeper the gradient of a distance-time graph, the ... the speed

  faster
• if an object is changing speed on a distance-time graph, you can find its speed at a point by...

  finding the gradient of the tangent to the curve at that point
• velocity-time graph

  line graph used to show how velocity changes over time
• velocity-time graph example

  
• the shape of a velocity-time graphs shows...

  how the velocity of an object is changing

  - gradient = acceleration

  - flat line = steady speed

  - uphill line = constant acceleration

  - downhill line = deceleration

  - curved line = changing acceleration/deceleration
• the steeper the lines on a velocity-time graph, the ... the acceleration/deceleration

  greater
• how do you calculate changing acceleration on a velocity-time graph?

  by dividing change in velocity by time taken
• the area under any section of a velocity time graph is...

  the distance travelled