Physical World & Measuring Speed and Acceleration

Distance Conversions

• 1 m = 100 cm
• 1 km = 1000 m
• Examples:
  • 70 cm = 0.7 m
  • 16 cm = 0.16 m
  • 4 km = 4000 m
  • 7.5 km = 7500 m

Time Conversions

• 1 minute = 60 s
• 1 hour = 3600 s
• Examples:
  • 5 minutes = 300 s

Units for Speed

• Metres per second: ms^{-1}

Speed Triangle

• D = distance
• S = speed
• T = time
• To calculate speed: speed = \frac{distance}{time}
• To calculate time: time = \frac{distance}{speed}
• To calculate distance: distance = speed \times time

Acceleration

• Formula: acceleration = \frac{final \ speed - first \ speed}{time \ taken \ for \ the \ change \ in \ speed}
• Units: m/s^2 or ms^{-2}
• 'From rest' implies the initial speed is zero.

Velocity

• Velocity includes both speed and direction.
• Units for velocity are the same as speed: m/s or ms^{-1}

Acceleration (Detailed)

• Rate of change in velocity (can be increase or decrease).
• Deceleration is negative acceleration.

Average Speed

• Formula: Average \ speed = \frac{distance}{time}
• Steeper slope on a graph indicates a larger speed value.