Emma Taila & Nicolas Petruzzelli Skydiving, Yo Emma Taila & Nicolas Petruzzelli

Scientific Method QUESTION: How does parachute size affect fall time? PREDICTION: When the size of the parachute increases, the fall time will decrease. EXPERIMENT: You would need to test different size parachutes (independent variable) & record the amount of time it takes for the skydiver to fall (dependent variable). Take multiple trials for each parachute height & average out the recorded times. PRESENT RESULTS: A data table with all the recorded trials & a graph that shows the relationship between the parachute size & fall time on the x & y axis, respectively. ANALYZE: The results should show a relationship between the variables. This relationship could be described as direct or inverse, and proportional. If the results contradict your original hypothesis you must change your thinking.

Motion Graphs The motion graphs track position, velocity, or acceleration over time. Time goes on the x axis & the other value goes on the y axis. The motion graphs for a skydiver would look like this:

Calculations Average velocity: the velocity over a period from the initial and final velocity (final v-initial v), divided by the change in time over that period; the average velocity over a period that begins before the skydive & ends once the skydiver reaches terminal velocity would be about 166 m/s Instantaneous Velocity: the velocity at one specific point in time, it is 2 times the average velocity when it is the final velocity & the initial velocity is zero; if you took the instantaneous velocity of a skydiver once they had reached terminal velocity, it would be about 200 km/s Acceleration: the change in velocity; a skydiver accelerates in free fall & later decelerates once the parachute is deployed

Newton’s First Law An object in motion will stay in motion unless acted on by another force and an object at rest will stay at rest unless acted on by another force. The main forces acting on a skydiver are gravity & air resistance. The skydiver will accelerate as a result of the force of gravity being greater than air resistance. The skydiver will stop accelerating once they reach terminal velocity and the forces of gravity and air resistance become balanced. Then, once the parachute is deployed, air resistance increases and the skydiver will slow down before again reaching a constant velocity as the forces are again balanced.

Free Body Diagram When skydiving the two major forces acting on you are gravity & air resistance. While in free fall the free body diagram would look like this to show downward acceleration: Once you reach terminal velocity & are no longer accelerating: When the parachute opens & you slow down:

Newton’s Second Law Fnet=mass*acceleration This is the equation used to determine the net force acting on an object. It can also be rearranged to show the relationship between any of the other variables. When skydiving, the skydiver accelerates because there is a downward net force acting on them as a result of gravity, and later they decelerate as a result of air resistance. When the forces become balanced, and the net force is zero, there is no acceleration. The skydiver always has mass, but they need a net force in order to accelerate.

Newton’s Third Law For every force there is an equal force in the opposite direction. When skydiving, as a person lands on the ground, force is exerted downward from the person’s landing onto the ground. The impact on the ground also causes force to be exerted back in an upward direction onto the person. The amount of downward force from the person is equal to the amount of upward force exerted from the ground.

Weight When skydiving weight is the amount of gravity of an object. When falling the weight of an object has no effect on the speed at which it falls, since the main force acting on it is gravity. Therefore if one person is heavier than another, they will fall at the same speed.

Law of Gravitation The force of attraction exists between any two objects and is the same for each one. As the force of gravity on an object decrease, the distance between two objects, such as a person falling towards the ground, increases. As the force if gravity of an object increases, mass of either object increases as well. Gravitational acceleration is 9.8

Momentum, Impulse, and Collisions Momentum is the characteristics of an object related to its mass and velocity. Impulse is the force onto an object that will affect its momentum. A collision is when two objects interact and exert force on each other. Each of these relate to skydiving because momentum is created as a person falls and increases speed, impulse is the air resistance since it affects the momentum of someone, and collisions occur when the person reaches the ground.

Energy The ability to create change in an object or cause it to do work. Is able to come in different forms and can also be changed from one form in an object to another. In a closed system the total energy is always constant. In skydiving, energy, in this case gravitational energy, is created as a person falls from the plane towards the ground.

Thermodynamics Thermal energy is the kinetic energy of the particles within an object. When the temperature in a closed system rises, the pressure increases. The higher up a person is in the atmosphere when skydiving, the more thermal energy they have.