The Physics of Skydiving Isa Hazeltine and Molly Kirkpatrick Period 3

Scientific Method In order to create an experiment about skydiving we need to use scientific method. This includes a question, hypothesis, experiment, comparison, and conclusion.

Here is an example to display scientific method in skydiving. How does the height of the airplane affect the speed of the skydiver? We believe that if the airplane is higher than the speed will be greater. For our experiment, we will have a skydiver jump from different heights and measure his/her speed. We will have multiple trials for each height and compare the data to find averages. Our independent variable will be the height and our dependent variable is the speed. We will display our data in a table and a graph. Based on our evidence, it will either support or not support our prediction. If it supports our prediction we can discover the relationship between the two variables. Based on the evidence, we can uncover limitations and new ways to refrain from error.

Motion Graphs Motion graphs describe either the position, velocity, or acceleration of an object in general terms. You have to pay attention to the direction the object is moving as well. We can use the position graphs to describe where the skydiver is in the sky relative to the ground. We can use the velocity and acceleration graphs to describe how fast the skydiver is falling and accelerating throughout his trip.

Calculations: average velocity, instantaneous velocity, acceleration We can use the velocity and acceleration equations to measure how fast the skydiver is falling when dropped from the different heights.

Newton’s First Law Newton's first law states that an object in motion will stay in motion unless acted upon by another force. And an object at rest will stay at rest unless acted upon by another force. Example: A skydiver will continue to fall until it is stopped by the ground. The ground acts as the outside friction force.

Free Body Diagram We can use Free Body Diagrams to predict and then describe the Net Force on the skydiver as they are falling.

Newton’s Second Law Newton's second law states that an objects net force is equal to its mass times its acceleration. Also known as Fnet=m*a. Example: If you wanted to find the force of the skydiver you would use this equation. If the skydiver was 50kg and moving at 9.8m/s2 then you would do 50*9.8. The net force would be 490N.

Newton’s Third Law For every force, there is an equal and opposite force. This means that two objects, no matter the mass, have the same force against each other. The object with the lesser mass will accelerate more. The forces are on two different objects so they do not cancel out. For example, when a skydiver is falling, the wind resistance against his parachute has the same magnitude force as the force of gravity. Although the forces have equal magnitude, the skydiver still falls because objects with a lesser mass will accelerate more due to the proportions of the equation in Newton’s Second Law.

Weight Weight = Force of Gravity (W = Fg) The force of gravity is NOT the same as gravitational acceleration. (9.8m/s2) Fg = mass * 9.8m/s2 Weight is NOT the same as mass. Weight is the force with which earth attracts an object and is measured in pounds. Mass is the amount of material in an object and measures the inertia or resistance to change in motion and is measured in kilograms. If a skydiver’s mass is 25kg, his gravitational acceleration is 9.8m/s2, so you multiply the 2 to find his weight. The skydiver weighs 245 pounds.

Law of Gravitation A force of attraction exists between any 2 objects; because of Newton’s Third Law, this force is the same on each object. The force of gravity increases as the mass of either increases. The force of gravity decreases as the distance between the objects increases. We can find the magnitude of the force of gravity on the skydiver depending on how far away he is from the ground. As he is falling, the force of gravity will increase as he is nearing the ground.

Momentum, Impulse, Collisions Momentum: p = m*v Momentum is mass in motion and is always conserved. Total magnitude of momentum stays the same before and after a collision. There's two different types of collisions: elastic and inelastic. Elastic collisions mean that the two objects bounce off each other after the action, inelastic means they stick together. Although they are different, they use relatively the same equation. Impulse: j = force*time A force that is applied for a given amount of time will change the momentum. The greater the impulse, the less force will be applied on the object. Parachutes increase the impulse of an object because they slow the force of gravity and increase the time the skydiver falls.

Energy Energy is an object’s ability to produce change. GPE: Gravitational Potential Energy depends on how far away the object is from the ground. GPE = m*g*h KE: Kinetic Energy depends on the object’s movement. KE = 1/2m*v2 In the airplane, the skydiver starts with a high GPE because he is the farthest from the ground he will be. He has no KE because he is not moving yet. as he jumps, his GPE decreases at the same rate the KE increases because energy is always conserved. The magnitude of the total energy will stay the same throughout the entire trip.

Thermodynamics Thermal energy is the kinetic energy of the particles in an object. Thermal energy is measured by the temperature of said object. When the temperature rises in a closed system, the pressure increases. Thermal energy only flows from high temperature to low temperature. The higher up the skydiver is, the cooler the air temperature is. The molecules are moving slower and there is less pressure. As the skydiver falls, the air temperature increases because the molecules are moving faster and there's greater pressure.