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Rocket

Theme A - Space, Time & Motion

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Thermometer

Theme B - The Particulate Nature Of Matter

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Water Wave

Theme C - Wave Behaviour 

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Magnifying Glass Tilted Right

Theme D - Fields

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Microscope

Theme E - Nuclear & Quantum Physics

First off, let&#39;s start with the basics. Projectile motion refers to the motion of an object that is thrown or projected into the air at an angle to the horizontal. Normally, when we talk about projectile motion, we assume there is no air resistance and the only force acting on the object is gravity. However, in the real world, air resistance (or drag) is a crucial factor that alters the motion of the object.

As presented in Figure 24, we see two trajectories - one showing the path of the object in a vacuum (where there is no air resistance), and the other showing the path when there is air resistance (drag force). The angle of projection is the same for both cases - 45&deg;.

Now, let&#39;s break down how air resistance impacts the motion

<ul>
	<li>Range is decreased: In the real world, when you throw a baseball, it won&#39;t go as far as it would in space (a vacuum). That&#39;s because air resistance slows it down mid-air. That&#39;s why when professional athletes throw or hit balls, they do so with more power to counteract the drag force.</li>
	<li>Trajectory is no longer parabolic: In a vacuum, the object would follow a neat, U-shaped path called a parabola. But here on Earth, air resistance messes with this perfect curve and alters the trajectory.</li>
	<li>Maximum height is reduced: Just as the range decreases, the highest point that the object can reach also reduces because of air resistance. Think of it like jumping with a parachute - the air resistance prevents you from going too high!</li>
	<li>Vertical acceleration is no longer constant: Without air resistance, the object would speed up towards the ground at a constant rate (9.81&nbsp;\(\frac {m}{s^2}\), thanks to gravity). But with air resistance, it slows down as it falls, making the acceleration decrease over time.</li>
	<li>Horizontal deceleration is introduced: In a vacuum, an object would keep moving horizontally without slowing down (because there&#39;s no force to slow it down). However, air resistance slows down the object&#39;s horizontal motion, which is why we see horizontal deceleration.</li>
	<li>Speeds are reduced: Overall, the object moves slower with air resistance. It&#39;s like running on a windy day versus a calm day. The wind (air resistance) makes it harder for you to run (move) quickly.</li>
	<li>Time of flight becomes complex: In a vacuum, you could easily calculate the time the object stays in the air. But with air resistance, the initial conditions (like the object&#39;s shape, size, and initial velocity) play a major role in determining the time of flight. So, it becomes more complex.</li>
</ul>

In conclusion, the real world is complicated! While it&#39;s nice and simple to assume no air resistance in physics problems, the reality is that air resistance plays a significant role in projectile motion. And as budding physicists, it&#39;s vital for us to understand these differences.

Comparing Trajectories: Vacuum Vs. Air Resistance (Figure 24)

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Higher Level

Physics HL

Theme A - Space, Time & Motion

Comparing Trajectories: Vacuum Vs. Air Resistance (Figure 24)

Table of content

Understanding projectile motion

Case study - comparing two different trajectories

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Theme A - Space, Time & Motion

Comparing Trajectories: Vacuum Vs. Air Resistance (Figure 24)

Table of content

Understanding projectile motion

Case study - comparing two different trajectories

Unlock the Full Content!