Physics

• How to calculate speed

  
• If the speed varies during a journey, how can the average speed be calculated


  Average speed =

  total distance travelled/ change in time
• Typical Speeds for normal things

  walking 2m/s

  running 4m/s

  cycling 6m/s

  wind speed 20m/s

  motor way speed limit 30m/s

  high speed train 90m/s

  airplane 270 m/s

  Sound 330 m/s
• Displacement


  -Is measured in a straight line

  -Is a vector quantity

  - For example, if runners are running a curved 200 metre track. The distance in a straight line from start to finish is displacement.
• Measuring Speed in a Lab


  1. Measure the distance between 2 points with a ruler or a tape measure

  2. Time how long it takes with a stopwatch

  OR

  1.Attach a card of known length to the object with a ruler

  2.As the object travels, card attached to it passes through a light gate . This gives the time it takes for the card to travel through

  3.Computer automatically calculates speed of card length data is entered before.
• Velocity


  -Measured in m/s

  -Speed in a particular direction
• Positive Velocity


  Object moving forward
• Negative Velocity


  Object moving backwards
• Vector Quantities


  displacement (m)

  velocity (m/s)

  acceleration (m/s²)

  force (N)

  momentum (Nm)
• Scalar quantities


  distance (m)

  speed (m/s)

  energy (s)

  pressure (Pa)

  mass (kg)

  temperature (k)
• Distance Time Graphs


  A graph where distance is plotted against time.

  From a distance time graph, we can calculate speed.
• Horizontal Line on a Distance Time Graph


  The object is stationary
• Straight, sloping lines on a Distance Time Graph


  The object is travelling at a constant speed

  The steeper the line, the faster the object is moving
• How do you find the speed for a distance time graph?


  Speed = gradient = change in distance / change in time
• Acceleration


  -Rate of change of velocity

  -Vector quantity
• Positive Acceleration


  The object is speeding up
• Negative Acceleration


  The object is slowing down
• How to calculate acceleration


  final velocity-initial velocity/time

  = a(v-u) /t
• Velocity Time Graph


  Shows how velocity is related to time
• Horizontal line on a velocity time graph


  Object is travelling at constant velocity

  The higher up the horizontal line, the higher the velocity
• Straight, sloping line on a velocity time graph


  Object is accelerating

  The steeper the line , the greater the acceleration
• Line slopes upwards on Velocity time graph


  Positive acceleration
• Line slopes downwards


  Negative acceleration
• How to calculate distance from a Velocity Time graph


  1. Split the area under the graph into shapes of squares and triangles.

  2. Calculate each distance separately

  3. Add all that up
• How to calculate acceleration from a Velocity Time Graph


  By using the gradient:

  a= (v-t)/t
• What are the two types of physical quantities discussed in the video?

  Scalar and vector quantities
• What defines a scalar quantity?

  A scalar quantity has only magnitude and no direction
• What is another term for magnitude?

  Size
• If a car travels at 22 meters per second, what is the magnitude of its speed?

  22 meters per second
• Why is speed considered a scalar quantity?

  Because it does not have a direction
• Name three examples of scalar quantities.

  Distance, mass, temperature
• What distinguishes vector quantities from scalar quantities?

  Vectors have both magnitude and direction
• List four examples of vector quantities.

  Velocity, displacement, acceleration, force
• How can you visualize the difference between scalar and vector quantities?

  • Scalars: Only magnitude (e.g., distance)
  • Vectors: Magnitude and direction (e.g., displacement)
• If you walk a distance of three kilometers without specifying a direction, what type of quantity is this?

  Scalar quantity
• What happens when you specify a direction while walking three kilometers?

  You provide a vector quantity
• How is a vector represented visually?

  With arrows indicating magnitude and direction
• What does the length of an arrow in a vector represent?

  The magnitude of the vector
• How would you represent a vector of four kilometers north?

  With an arrow pointing north, four units long
• What does a negative vector indicate?

  It indicates a direction opposite to the positive direction