Physics Y9 P1

• Speed


  Distance (in metres) divided by time (in seconds)
• Calculating speed


  Distance / Time

  
• Formula triangle


  Graphical representation of the speed, distance and time formula
• Using the formula triangle

  Distance = Speed x Time
• Interpreting a distance-time graph

  1. Flat line = constant speed

  2. Curved line = changing speed

  3. Upward curve = acceleration

  4. Downward curve = deceleration
• Gradient of a distance-time graph

  Represents the speed of the object
• Balanced forces cause no change in motion
• Unbalanced forces cause a change in motion (acceleration)
• Force


  A push, pull or twist
• Resultant force


  The sum effect of more than one force
• Friction opposes motion and tries to slow down moving objects
• Air resistance is a type of friction caused by objects moving through air
• Air resistance


  • Depends on size, shape and speed of the object
  • Can be reduced by using a more streamlined shape
• Terminal velocity


  The constant speed reached when the upward air resistance force balances the downward weight force
• Reaching terminal velocity


  1. Speed increases at start

  2. Air resistance increases until it balances weight

  3. Parachute opens, speed decreases to new lower terminal velocity
• Mass


  The amount of matter in an object, same anywhere in the universe
• Weight


  The force exerted on an object by gravity, varies depending on location
• Mass and weight are not the same
• Gravity


  An attractive force that acts between all masses, depends on mass and distance
• Gravity causes objects to orbit larger masses like planets orbiting the Sun
• Rocket motion


  1. Gravity force decreases as rocket gets further from Earth

  2. Rocket mass decreases as fuel is burned
• Planets are natural satellites of the Sun