P9

• What do distance-time graphs allow us to visualize?

  How far something has traveled over time
• What does the gradient of the line on a distance-time graph represent?

  The speed of the object at that time
• What is the formula for speed in terms of distance and time?

  Speed = change in distance / change in time
• What does a flat line on a distance-time graph indicate?

  The object is stationary
• What does a steeper line on a distance-time graph indicate?

  The speed is increasing
• What does a decreasing gradient on a distance-time graph indicate?

  The object is decelerating
• How do you find the speed at a particular point on a curve?

  Draw a tangent to the curve at that point
• What is a tangent in relation to a curve on a graph?

  A straight line touching the curve at one point
• How do you calculate the gradient of a tangent?

  By dividing change in distance by change in time
• What do straight lines, flat lines, and curved lines represent on a distance-time graph?

  • Straight lines: Constant speeds
  • Flat lines: Stationary
  • Curved lines: Changing speeds
• What should you do if the point lies on a straight line?

  Calculate the gradient of the line
• What should you do if the point lies on a curve?

  Draw a tangent and calculate its gradient
• What are the key points to remember about distance-time graphs?

  • Straight lines: Constant speed
  • Flat lines: Stationary
  • Curved lines: Changing speed
  • Use tangent for speed on curves
• What are the two types of quantities discussed?

  Scalar and vector
• What is a scalar quantity?

  It only has magnitude
• How is speed classified?

  As a scalar quantity
• Give an example of speed.

  A person running at 4 m/s
• What is velocity classified as?

  As a vector quantity
• Provide an example of velocity.

  A person cycling 6 m/s east
• Why is it common to confuse speed and velocity?

  They are often used interchangeably
• What is distance classified as?

  As a scalar quantity
• What does displacement include that distance does not?

  Direction
• How do you calculate the speed of a train crossing a bridge?

  Distance divided by time
• What is the speed of a train that crosses a 550 m bridge in 10 seconds?

  $55 \text{ m/s}$
• How does velocity differ from speed in terms of units?

  Velocity includes direction in units
• What does the symbol 's' represent in the velocity equation?

  Displacement
• What does the symbol 'd' represent in the speed equation?

  Distance
• What does 't' represent in both equations?

  Time
• Why do people often use the velocity equation incorrectly?

  They may not have a direction
• What is the benefit of using velocity?

  It can represent negative values
• What do we calculate when objects vary in speed?

  Average speed or average velocity
• What is the average walking speed of a person?

  About 1.5 m/s
• What is the average running speed of a person?

  About 3 m/s
• What is the average cycling speed of a person?

  About 6 m/s
• What is the average speed of a car on the main road?

  About 25 m/s
• What is the average speed of a fast train?

  About 55 m/s
• What is the speed of sound waves in air?

  About 330 m/s
• How does the speed of sound change in different mediums?

  It varies depending on the medium
• What factors can affect wind speed?

  Temperature, pressure, and structures
• What can wind speed vary from?

  Almost zero to faster than a train