The rationale for this investigation

Introduction There are various factors that affect the rate of descent of a parachute e. g. the weather at the time of descent, the height from which the parachute begins its descent, the type of material. The focus of this investigation is on two factors, which are known to affect the rate of descent of a parachute;  The surface area of the parachute. The mass of the parachute, including its parachutist. Theoretical background The rationale for this investigation derives from Newton’s second law of motion, F= ma where F represents force, m represents mass and a represents acceleration.

Without the influence of air resistance, all objects accelerate at the same rate 10m/si???. This is because the force of an object depends on its mass. For example, if we take a rock with a mass of 10kg and one with a mass of 1kg we find that they land at the same time. The force of a falling object when there is no air resistance is 10 x m so in this case the force of the 10kg rock is 100N (Newtons) and the force of the 1kg rock is 10N. If we put these figures into the equation for acceleration, a = F we find that the acceleration of the two rocks is equal. (10m/si??). m Hypothesis This investigation predicts that.

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1) The larger the surface area of the parachute, the slower the average rate of descent 2) The greater the mass, the faster the average rate of descent How the surface area of an object affects its rate of descent The actual amount of air resistance is dependent on two factors, the speed of the falling object and the cross-sectional area of the object. As an object falls through the air, it almost always encounters some degree of air resistance. Air resistance is the result of collisions of the object’s leading surface area (the area of the side, which hits the floor) with air molecules.

The larger the surface area, the more collisions of particles there will be with the object, causing it to slow down. If there are two parachutes (of the same mass), one with an area of 10 metres and the other 5 metres, the 10-metre parachute will encounter more collisions with air particles. The collisions will cause the parachute to slow down. How the mass of an object affects its rate of descent As mentioned above, the amount of air resistance depends on the speed of the falling object. Objects will continue to accelerate to higher speeds until they encounter an amount of air resistance, which is equal to their weight.

A parachutist with parachute together weighing 150kg, experience a greater force of gravity due to their larger mass (f = 10m) than a parachutist with parachute weighing 100kg. It will therefore accelerate to a higher speed before reaching a terminal velocity. To help with this investigation, the principle of terminal velocity needs to be applied. As an object falls, it picks up speed. This increase in speed leads to an increase in the amount of air resistance. Eventually the force of air resistance (the upward force) becomes large enough to balance the force of gravity (the downward force).

The change in velocity terminates as a result of the balance of forces. At this time the net force is 0 N. Newton’s first law tells us that objects will not accelerate if the net force is 0N. The more massive the object the higher its speed will be until it encounters terminal velocity. Therefore, more massive objects fall faster than less massive objects because they are acted upon by a larger force of gravity. For this reason they accelerate to higher speeds until the air resistance equals the force of gravity According to this theory, the heavier the object, the faster the rate of descent.

Method Equipment: Stop watch- I have chosen this method of timing because it is accurate and easy to use. Bin bags- they are a very flexible material and move through the air well. Masses- to change the weight of the parachute, String- it is light and easy to use. I intend to test the prediction by timing the fall of parachutes. For the first experiment I will use different surface areas and for the second I will use different masses. I will use a stopwatch to time it so it is accurate and I will drop it from a 2-metre mark on the blackboard.

I plan to do six examples for each factor, do each measurement three times and then find the average time. This will ensure a greater accuracy as one can obtain a more accurate average speed by doing many examples. When doing an experiment it is very important to keep all factors except from the one you are investigating the same to ensure the most accurate results. Preliminary experiment Aim: To test the methodology and to explore whether the intended parachute sizes gives easily measurable decent times with sufficient variation to detect a trend.