SP2

• scalars


  only have magnitude and not direction

  e.g. mass, distance, speed, energy, volume, density, temperature, power
• vectors


  both magnitude and direction

  e.g. displacement, velocity, weight, force, acceleration, momentum
• comparing scalars and vectors


  the two can be quite similar and can correspond(E.g. distance and displacement, speed and velocity)
• speed


  the distance an object travels every second. It is a scalar quantity
• speed equation


  constant speed is calculated

  where speed is in metres per second - m/s

  distance in metres - m

  time taken in seconds - s

  
• calculating average speed


  in some cases the speed of a moving object is not constant. For example, the object may change speed at certain moments.

  
• Velocity


  is similar to the speed of an object, except it also describes the direction
• distance time graphs


  how the distance an object moving in aa straight line varies over time
• constant speed on a distance time graph


  a straight line represents constant speed, the slope of the straight line represents the magnitude (very steep= large speed, shallow=small speed, horizontal=stationary)
• changing speed on a distance time graph


  this is represented by a curve, if the slope is increasing then the speed is increasing, if the slope is decreasing the speed is decreasing

  
• Gradient of a distance time graph


  the speed of a moving object can be calculated from the gradient of a line.

  the rise is the change in y (distance)

  the run is the change in x (time)

  
• acceleration


  the rate of change in velocity

  • a = acceleration in metres per second squared (m/s2)
  • Δv = change in velocity in metres per second (m/s)
  • t = time taken in seconds (s)

  
• acceleration equation 


  can also be shown as

  a=v-u/t

  change in velocity = final velocity − initial velocity

  Δv = v − u
• freefall


  the absence of air resistance, all objects fall with the same acceleration

  • This is called the acceleration due to gravity:

  g = acceleration due to gravity = 10 m/s2
• estimating accelerations


  The acceleration of an object is a measure of how quickly its velocity changes

  
• calculating uniform acceleration

  (final speed)2 − (initial speed)2 = 2 × acceleration × distance travelled

  • Where:
  • x = distance travelled in metres (m)
  • u = initial speed in metres per second (m/s)
  • v = final speed in metres per second (m/s)
  • a = acceleration in metres per second squared (m/s2)

  
• Velocity-Time Graphs

  • A velocity-time graph shows how the velocity of a moving object varies with time
  • The red line represents an object with increasing velocity
  • The green line represents an object with decreasing velocity

  
• Acceleration on a Velocity-Time Grap


  straight line represents constant acceleration. The slope of the line represents the magnitude of acceleration

  • A steep slope means large acceleration (or deceleration)
  • A gentle slope means small acceleration (or deceleration) - i.e. the object's speed changes very gradually
  • A flat line means the acceleration is zero
• Gradient of a Velocity-Time Graph


  The acceleration of an object can be calculated from the gradient of a velocity-time graph

  
• Area under a Velocity-Time Graph


  area under a velocity-time graph represents the displacement (or distance travelled) by an object
• typical speeds


  in m/s

  
• measuring speed


  ensure that the result for speed is accurate, choose the appropriate equipment to measure distance and time

  
• compare the average falling speed of a tennis ball to a plastic cone


  • A metre rule could be used to measure the distance they fall from
  • A timer could be used to measure how long they take to reach the ground
• measuring long distances


  use a trundle wheel
• Using Lights Gates to Measure Time

  Light gates are pieces of digital equipment that allow times to be measured more accurately

  
• Newton's First Law of Motion

  Objects will remain at rest, or move with a constant velocity unless acted on by a resultant force
• resultant force is not 0


  the speed of the object can change

  the direction of the object can change
• Applying Newton's First Law


  Newton's first law is used to explain why things move with a uniform velocity. If the forces acting on an object are balanced, then the resultant force is zero.

  The velocity (i.e. speed and direction) can only change if a resultant force acts on the object
• Newton's Second Law


  The acceleration of an object is proportional to the resultant force acting on it and inversely proportional to the object's mass
• Calculating Force & Acceleration

  newtons second law can be expressed as$f=$$ma$

  • Where:
  • F = resultant force on the object in Newtons (N)
  • m = mass of the object in kilograms (kg)
  • a = acceleration of the object in metres per second squared (m/s2)

  
• Newton's Third Law


  each action has a eqal and opposite reaction