1.3
Learning Target: Acceleration measures how fast velocity changes.
Learning Target: Acceleration measures how fast velocity changes.
Review:
- Speed describes how far an object travels in a given time.
- Velocity is a measure of the speed and direction of motion.
Describe the speed from start to finish of Christian Yelich's home run ball.
As the ball rises, it slows down. Then, as the ball falls back toward the ground it speeds up again. When the ball hits the seats, its direction of motion changes and it bounces back up into the air. The speed and direction of the ball do not stay the same as the ball moves. The ball's velocity keeps changing.
You can find out how much an object's position changes during a certain amount of time if you know its velocity. The rate at which velocity changes with time is called acceleration.
The word acceleration is commonly used to mean "speeding up". In physics acceleration refers to any change in velocity. A driver slowing down to top at a light is accelerating. A runner turning a corner is also accelerating because the direction of her velocity is changing as she turns.
Three types of acceleration:
Positive Acceleration
Positive Acceleration
- Increase in velocity
- Speeding up
- Decrease in velocity
- Slowing down
- Also called, deceleration
- Car changes direction but not speed
Calculating Acceleration
If you know the starting velocity of an object, the final velocity, and the time interval during which the object changed velocity, you can calculate the acceleration of the object.
If you know the starting velocity of an object, the final velocity, and the time interval during which the object changed velocity, you can calculate the acceleration of the object.
When the final velocity is less than the initial velocity the answer will be negative. The negative sign indicates a negative acceleration - that is, an acceleration that decreases the velocity.
Velocity over time can also be graphed. A line rising vertically shows an increase in acceleration. A line going horizontally shows zero acceleration. A line going down shows a decrease in acceleration. (deceleration)
Increasing = positive acceleration
Decreasing = negative acceleration
Increasing = positive acceleration
Decreasing = negative acceleration