Air Resistance

Definition

Air resistance, also known as drag, is the force that opposes the motion of an object moving through the air. It is a type of friction force that acts on objects in motion, slowing them down and affecting their trajectory.

5 Must Know Facts For Your Next Test

1. Air resistance increases with the square of an object's velocity, meaning that doubling the speed quadruples the air resistance.
2. The shape of an object, as described by its drag coefficient, significantly affects the amount of air resistance it experiences.
3. Air resistance is a major factor in the motion of projectiles, causing them to deviate from their ideal parabolic trajectories.
4. Streamlining an object, such as a car or aircraft, can significantly reduce air resistance and improve its energy efficiency.
5. Terminal velocity is the maximum speed an object can reach when the force of air resistance equals the force of gravity, causing the object to stop accelerating.

Review Questions

• Explain how air resistance affects the motion of a projectile in the context of projectile motion.
  • In the context of projectile motion, air resistance acts as a force that opposes the motion of the projectile, causing it to deviate from its ideal parabolic trajectory. Air resistance increases with the square of the projectile's velocity, meaning that as the projectile moves faster, the air resistance force becomes more significant. This air resistance force causes the projectile to slow down, change direction, and ultimately reach the ground sooner than it would in the absence of air resistance.
• Describe how the shape of an object, as represented by its drag coefficient, affects the air resistance it experiences.
  • The shape of an object, as described by its drag coefficient, is a crucial factor in determining the amount of air resistance it experiences. Objects with a more streamlined, aerodynamic shape tend to have a lower drag coefficient, meaning they encounter less air resistance as they move through the air. Conversely, objects with a less streamlined shape have a higher drag coefficient, resulting in greater air resistance and more energy being required to overcome it. Optimizing the shape of an object to minimize its drag coefficient is an important design consideration in various applications, such as in the development of high-performance vehicles or aircraft.
• Analyze the relationship between an object's velocity and the air resistance it experiences, and explain how this relationship affects the object's terminal velocity.
  • The relationship between an object's velocity and the air resistance it experiences is a key factor in understanding the concept of terminal velocity. Air resistance increases with the square of the object's velocity, meaning that as the object moves faster, the air resistance force becomes more significant. This relationship leads to the object reaching a maximum velocity, known as the terminal velocity, where the force of air resistance exactly balances the force of gravity acting on the object. At this point, the object stops accelerating and maintains a constant velocity. The terminal velocity of an object is influenced by factors such as its mass, shape, and the density of the surrounding air, with more streamlined objects and lighter objects generally reaching higher terminal velocities.

Related terms

Drag Coefficient: A dimensionless quantity that describes the shape of an object and its effect on air resistance. It is used to calculate the drag force on an object.

Terminal Velocity: The maximum velocity an object can reach when the force of air resistance equals the force of gravity acting on the object, causing it to stop accelerating.

Streamlining: The process of designing an object's shape to minimize air resistance, allowing it to move more efficiently through the air.