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### Course: Middle school physics>Unit 2

Lesson 2: Activity: How can a skydiver fall safely?

# Activity: How can a skydiver fall safely?

Make science come alive in your classroom with this free hands-on activity aligned to middle school NGSS standards.
You can print this activity, or assign it through a digital classroom!

### The challenge

Imagine you are in an airplane 4,000 feet above the ground. You have a parachute packed on your back. You take a deep breath and then…you jump out! Down you go!
Jumping out of an airplane may seem like a scary idea, yet skydivers land on the ground at a safe speed every day. How is this possible? In this activity, students will use coffee filters and their knowledge of forces and motion to develop an explanation.

### Overview

This activity is designed to be completed in two 45-minute class periods, with additional time required for follow-up creative projects. The activity consists of the following parts:
• Setting the stage—Students review the fundamentals of forces and gravity, as well as develop an understanding of air resistance. (10 minutes)
• Investigation (Part 1)—Students drop open and crumpled coffee filters and compare their motions. Students use their observations to draw conclusions about the relative strengths of the forces on each filter. (10 minutes)
• Investigation (Part 2)—Students nest and drop increasing numbers of coffee filters together. Students use Newton's second law to explain the different motions observed in each case. (25 minutes)
• Let's get creative!—Students apply their knowledge to create an informational poster for skydivers explaining why they will reach terminal velocity, which allows them to land safely. (45 minutes).
• Keep creating!—Students can choose from additional project ideas. Each project encourages students to combine scientific knowledge with creativity to produce something new.

### Give us feedback!

Have you tried this activity? Tell us your thoughts in this short survey.

## Want to join the conversation?

• once the skydiver reaches terminal velocity, why does he continue to fall? shouldn't he stop moving?
• When a skydiver reaches terminal velocity, all it means is that he stops falling faster. His rate of descent will not increase. He is still falling, but the speed he is falling as will not change as long as he doesn’t move.(edit: if he moves, the air resistance will change, and he will either slow down or speed up to match the air resistance, reaching terminal velocity again, and fall at a constant speed.) hope this clarifies things a little! :)
• So when the skydiver with a parachute dives will he go faster and faster until he pulls the parachute? Does he every slow down?
• When a skydiver jumps out of a plane, they initially accelerate due to the force of gravity. As they fall, their speed increases, and they continue to accelerate until they reach what's called their "terminal velocity."

Terminal velocity is the maximum speed at which the skydiver can fall through the air. It occurs when the force of air resistance (also known as drag) pushing against the skydiver equals the force of gravity pulling them downward. At this point, the net force acting on the skydiver becomes zero, and they no longer accelerate. Terminal velocity varies depending on factors such as the skydiver's body position, weight, and the density of the air.

Once the skydiver reaches terminal velocity, their speed remains constant unless something changes. For example, if the skydiver changes their body position to increase or decrease their surface area relative to the direction of motion, it can affect their terminal velocity.

When the skydiver pulls the parachute, it significantly increases their surface area, which greatly increases air resistance. This sudden increase in air resistance slows the skydiver down, causing them to decelerate rapidly. The parachute's design and the skydiver's technique determine the rate at which they slow down.

In summary, a skydiver initially accelerates due to gravity, reaches terminal velocity where their speed stabilizes, and then decelerates when they deploy the parachute. Throughout the skydive, the forces of gravity and air resistance continuously interact to determine the skydiver's speed and motion.
• Is there a greater pull higher or lower from the ground.
• There is a greater pull lower to the ground, as gravity follows the inverse square law. If you are twice as far from the Earth as you were a little while ago, gravity is 1/4 as strong as it was.
• Lets say that a skydiver (with a parachute) jumps into an endless hole without air friction, how far would they have to fall for the parachute not to make any difference in slowing them down? (note, the skydiver will not die from fall damage because the hole is endless)
• So, if the air was thicker terminal velocity would be less
• What does terminal velocity depend on?
• I still don’t understand,shouldn’t the skydiver surface area slows him down?
• Air resistance is not large enough to slow a skydiver down.
• I've always wanted to do the experiment where you have to create something to protect an egg from a certain height.
(1 vote)
• Waffles or Pancakes? Which one do you like better and why?
(1 vote)
• If two objects have the same mass, say the mass of 200,000 Kg are maybe 20 feet away from each other, would they still have a pull?
• Great Quesetion!

Yes, if two objects have mass, they will exert a gravitational pull on each other, regardless of the distance between them. This is described by Newton's law of universal gravitation, which states that the gravitational force between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

So, even if two objects have the same mass (let's say 200,000 kg each) and they are 20 feet away from each other, they will still exert a gravitational pull on each other. However, the strength of this gravitational force would be determined by the masses of the objects and the distance between them.

In this scenario, the force of gravity between the two objects would be weaker compared to if they were closer together. As the distance between the objects increases, the gravitational force between them decreases according to the inverse square law. Nevertheless, there would still be a gravitational attraction between the two objects, albeit weaker at a greater distance.

Hope this helps