Acceleration describes how an object's velocity changes over time.
Positive acceleration can mean speeding up or slowing down, depending on context.
Negative acceleration (deceleration) can also mean either speeding up or slowing down.
Determining Speeding Up or Slowing Down
Analyze the initial velocity and acceleration's sign.
Same Direction: If the acceleration and velocity vectors point in the same direction (e.g., both negative or both positive), the object is speeding up.
Opposite Directions: If the acceleration and velocity vectors point in opposite directions (e.g., velocity positive, acceleration negative), the object is slowing down.
Examples Explained
Negative Initial Velocity (-5 m/s) with Negative Acceleration (-10 m/s²)
Both vectors are in the same direction (backwards), leading to speeding up.
Acceleration pulls the velocity vector backwards, increasing speed.
Positive Initial Velocity with Negative Acceleration (-10 m/s²)
Vectors are in opposite directions (forward velocity, backward acceleration), leading to slowing down.
Acceleration decreases the forward velocity by pulling backwards.
Important Reminders
Acceleration alone doesn't determine if an object is speeding up or slowing down.
Always consider the initial velocity's direction and compare it with the acceleration's direction.
Understanding these concepts helps in solving problems related to motion and velocity changes effectively.
Conclusion
Recognizing the relationship between acceleration and initial velocity is crucial to correctly interpreting motion changes.
Future examples and practice in class will further reinforce these concepts.