Two Chapter 2

• Uniform Velocity - equal displacments in equal intervals of time.

• Only use this formula when velocities do not change.
• uniform velocity rarely occurs
• This equation can be used as average velocity.

• Straight lines on a position time graph indicate uniform velocity.
• Curved lines on a position time graph indicates accelerated motion
• If the curve is upwards, then acceleration is + or right or up.

• If the curve is downwards then acceleration is - or left or down.

• The slope of the position time graph is velocity.

• positive slope is motion right or up.
• negative slope is motion left or down.

• As previously stated:
• Average velocity = instantaneous velocity when motion is uniform. Otherwise, for non-uniform motion, average velocity is not necessarily equal to instantaneous velocity.
  • e.g. A car travels 1.0 km at 50 km/h[E], and 1.0 km at 100 km/h[E]. What is the average velocity?

• The average velocity equals the slope of the line joining the initial position and final position on a position time graph.

• Instantaneous Velocity - The velocity at an instant in time.
• If the velocity is not constant, then the slope of the position time graph is not constant and therefore velocity changes.

• At different instances in time, Velocity will be different.
• To find the instantaneous velocity, we need to find the slope of the postition time graph at an instant in time.

• As we take the slope of lines A & B etc., they will have slopes that tend towards the slope of the line C, the tangent at time T. The slope of the tangent at time T measures the steepness of the curve at time T (The instantaneous velocity).
• Instantaneous velocity is therefore the slope of the tangent to the curve at the time of concern.
  • Note how as we move from A to B etc., DT decreases, therefore:

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October 28, 2013