Forces in motion

• Newton's first law:

  • an object will remain in the same state of motion unless acted on by an external force.
• This tendency for objects to continue in the same state of motion is called inertia.
• Distance-Time Graphs

  If an object is accelerating, the distance-time graph will be a curve.

  For an accelerating object, its speed at a particular time is found by:

  • drawing a tangent to the curve at the point in time
  • working out the gradient of the tangent.
• Velocity = speed of an object in a given direction.
• Velocity:

  • When travelling in a straight line, an object with constant speed also has constant velocity.
• Velocity:

  If the object is not travelling in a straight line, e.g. it is turning

  a corner:

  • the speed can still be constant
  • the velocity will change, because the direction has changed.
• Velocity-

  An object moving in a circle:

  • is constantly changing direction, so it is constantly changing velocity
  • is accelerating even if it is travelling at constant speed.