Forces and motion 2

• What Is the equation for calculating speed?

  Speed = distance/time
• What Is the difference between speed and velocity?

  Speed only has size (scalar), velocity is speed in a particular direction (vector)
• What are typical speeds for walking, running and cycling?

  • 1.5 m/s
  • 3 m/s
  • 6 m/s (respectively)
• How can you calculate speed from a distance-time graph?

  Gradient (change in y / change in x)
• What Is acceleration?


  Change in velocity (could be change in speed and/or direction)
• What is the unit for acceleration?

  direction m/s
• What is the acceleration of a free falling object due to gravity?

  9.8 m/s
• What is the equation which links acceleration, change in velocity and time?

  acceleration (m/s^2) = change in velocity (m/s) ÷ time (s)
• How can you calculate acceleration from a velocity-time graph?


  Gradient (change in y/change in x)
• How can you calculate distance travelled from a velocity-time graph?

  area under the line
• What is the equation that links acceleration, force and mass?

  Force (N) = mass (kg) x acceleration (m/s^2)

  F= mxa
• HT only What is name of the tendency of an object to remain in a steady state (at rest or moving at the same speed and direction)?

  Inertia
• HT only What is the inertial mass of an object?

  How difficult it is to change an object's velocity
• HT only What does the acceleration of an object depend on?

  F= mxa

  Acceleration is directly proportional to force

  Acceleration is indirectly proportional to mass
• What does Newton's first law state regarding objects with no resultant force (balanced) acting on them?

  Object will remain still or moving at a constant speed in a constant direction
• What does Newton's second law state regarding objects with a resultant force (unbalanced) acting on them?

  Object will change speed and/or direction
• What does Newton's third law state?

  When two objects interact they exert equal and opposite forces on each other
• What is the name of the frictional force acting on a moving object?

  Drag
• In which direction does drag act on an object?

  In opposite direction to movement
• What happens to drag force when speed increases?

  Drag increases
• What effect does a larger surface area have on drag?

  Increases drag
• What can be done to reduce drag?

  Streamlining
• If an object is moving at a constant speed, what does this tell us about the forces acting on object?

  Forces are balanced (drag force = driving force/weight)
• What is the name of the maximum constant speed reached by falling/moving objects

  because drag force = weight/driving force?

  Terminal velocity