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How does the surface area of a parachute affect the rate of descent of a…
How does the surface area of a parachute affect the rate of descent of a falling object?
Physics Understanding
Gravity - The force accelerating objects on earth downwards, with an acceleration of 9.8m/s/s.
Air resistance - AKA drag, the force that opposes the movement of an object moving through the air. Formula: D = 1/2
ρ
v²
A
Cd
Terminal Velocity - The velocity at which gravity & drag are equal, leading to a constant velocity of the object's movement.
Newton's Second Law - acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. Formula: F = ma
Variables
Independent Variable: Parachute surface area
Justification: This is the factor being deliberately changed to observe its effect on the descent. Different parachute sizes will produce varying amounts of air resistance.
Method & Feasibility: This factor will be tested by using paper parachutes of varying sizes for the experiment. This factor has a high feasibility, as production of these paper parachutes is cheap & not skill-intensive.
Dependent Variable: Descent Time
Justification: This is the outcome being measured. It shows how the parachute’s surface area affects how slowly or quickly the object falls.
Method & Feasibility - This factor will be tested by measuring the time between the object's release & the object making contact with the ground. This will be done with a stopwatch. The feasibility of this is high, as very little equipment or experience is required to perform this.
Controlled Variables:
Mass of Object
Justification: Ensures that changes in descent speed are due only to parachute size, not varying weights.
Method & Feasibility: in all trials, the same metal weight, with 25g of mass will be used. This is feasible as such a weight is cheap to acquire & can be measured on a scale to ensure accurate mass.
Drop Height
Justification: Provides consistent conditions for comparing fall times across trials.
Method & Feasibility: This will be kept constant by choosing a specific height, from which all trials will be dropped. This is feasible because a low drop height (e.g. 1 m ) can be easily measured.
Parachute Material
Method & Feasibility: This variable will be kept constant by using standard size & shape ( a3, a4, a5, a6) paper, which can be bought or created (by halving a larger piece of paper) easily,
Justification: Different materials could affect air resistance, so these must remain constant to isolate the effect of surface area.
Parachute shape
Method & Feasibility: Parachute shape will be maintained by using the same shape of paper (a-series) & attaching paper to the weight from all 4 corners.
Justification: Different parachute shape would affect the drag coefficient, which would impact air resistance.
Environmental conditions
Method & Feasibility: The experiment will be conducted indoors, with no air currents (air conditioner, fan, opened windows) in the same location for all trials. Feasibility is high, as all that is needed is a room with closable or no windows.
Justification: Wind or varying air conditions can influence results, so the experiment should be conducted indoors or in still air.
Risk Factors
Falling Object
Justification: Strings or materials on the floor may cause someone to trip.
Mitigation: Keep the testing area tidy. Secure or remove loose strings, and lay out materials in a designated area.
Equipment Handling
Justification: Cutting parachute material may lead to cuts if tools are used improperly.
Mitigation: Use scissors carefully & store tools safely.
Tripping Hazards
Justification: Dropping weights from a height may injure people or damage surfaces if not controlled.
Mitigation: Ensure the drop zone is clear of people and fragile items. Use a soft landing surface (e.g. a mat or padding) and conduct the experiment in a safe, open area.