What is Acceleration? Definition & Examples

📚 Quick Study Guide: Understanding Acceleration

• 🚀 Definition: Acceleration is the rate at which an object's velocity changes over time. This change can be in speed, direction, or both!
• 📏 Vector Quantity: Unlike speed, acceleration is a vector. This means it has both a numerical value (magnitude) and a specific direction.
• 📝 Formula: The most common formula for average acceleration is $a = \frac{\Delta v}{\Delta t}$, where $\Delta v$ is the change in velocity ($v_f - v_i$) and $\Delta t$ is the change in time.
• ⏳ Units: The standard SI unit for acceleration is meters per second squared ($ \text{m/s}^2 $), which indicates how many meters per second the velocity changes each second.
• ➡️ Types of Acceleration:
  • ⏩ Positive Acceleration: When an object speeds up in the direction of its motion.
  • ⏪ Negative Acceleration (Deceleration): When an object slows down, or speeds up in the opposite direction of its initial motion.
  • 🌀 Centripetal Acceleration: Occurs when an object changes direction, even if its speed remains constant (e.g., an object moving in a circle).
• 💡 Key Concept: An object accelerates if it speeds up, slows down, or changes direction. If its velocity is constant (constant speed AND constant direction), its acceleration is zero.
• 🌍 Gravity's Role: On Earth, objects in free fall (neglecting air resistance) experience a constant downward acceleration due to gravity, approximately $g \approx 9.8 \text{ m/s}^2$.

🧠 Practice Quiz: Test Your Knowledge!

1. What is the fundamental definition of acceleration?
   1. The total distance covered by an object.
   2. The rate at which an object's position changes.
   3. The rate at which an object's velocity changes.
   4. The force acting on an object.
2. Which of the following units correctly represents acceleration?
   1. meters per second ($ ext{m/s}$)
   2. meters ($ ext{m}$)
   3. seconds ($ ext{s}$)
   4. meters per second squared ($ ext{m/s}^2$)
3. An object is moving at a constant speed in a straight line. What is its acceleration?
   1. Positive
   2. Negative
   3. Zero
   4. Constant but non-zero
4. A car speeds up from rest to 60 km/h in 10 seconds. In this scenario, the car is undergoing:
   1. Negative acceleration
   2. Zero acceleration
   3. Positive acceleration
   4. Constant velocity
5. A ball is thrown straight up into the air. At its highest point, just before it starts to fall back down, what is its acceleration (ignoring air resistance)?
   1. Zero
   2. Upwards, positive
   3. Downwards, approximately $9.8 \text{ m/s}^2$
   4. Constant velocity downwards
6. Which of the following scenarios describes an object experiencing centripetal acceleration?
   1. A car parked on a hill.
   2. A rocket launching straight up into space.
   3. A satellite orbiting Earth at a constant speed.
   4. A book sliding down a ramp.
7. A skateboarder increases their speed from $2 \text{ m/s}$ to $10 \text{ m/s}$ in $4 \text{ seconds}$. What is their average acceleration?
   1. $0.5 \text{ m/s}^2$
   2. $2 \text{ m/s}^2$
   3. $8 \text{ m/s}^2$
   4. $12 \text{ m/s}^2$