Parachutes Coursework

Thirdly we will attach a lump of plasticine to the ends of the strings of each parachute. The lump of plasticine must be put on at exactly the same point on the strings on each parachute so that the out come isn't affected by the parachutes being pulled down awkwardly or the strings being longer/shorter so that the parachute touches down quicker/slower. The plasticine should also be exactly the same mass (5grams) for each parachute because if there is more weight on some of the parachutes those parachutes will be pulled down faster and if there is less weight on some of the parachutes those parachutes will be pulled down slower. The plasticine must also be stuck at the same point on each of the parachute's strings so that the results aren't affected by the parachute being pulled down awkwardly or the strings don't vary in length.

Once all of the parachutes are made we will drop each parachute from the ceiling, which is 2.5m high, and time how long it takes for the parachute to hit the ground. The parachutes will be dropped from the same height each time so that the results are accurate, if some parachutes were dropped from different heights then the ones that were dropped from higher hights would take longer to get to the ground than ones dropped from lower hights because they would have a longer distances to travell. Dropping the parachutes from the ceiling will be easier because then we won't have to use the meter rule to measure the height every time we drop a parachute. We are going to drop each parachute 4 times so that an average can be taken so that the results will be more accurate because errors should be cancelled out.

The thing that we are going to controll in this experiment is the surface area of the parachutes being dropped. The thing that we are going to be measuring is the time it takes for parachutes of varying surface areas to travel 2.5m downwards. To make our experiment a fair test we will: drop the parachutes from the same height each time, keep the weight on the end of the parachute the same, keep the strings on the parachutes the same length, put the plasticine at the same pointon the strings on the parachute and secure the strings in the same position on each parachute. The reasons for these are explained earlier in the plan.

To make sure the experiment was safe we didn't stick our heads in the plastic bags (so we didn't suffocate), we were carefull with the scissors (so we didn't cut ourselves), we took high heeled shoes of when we were climbing on tables (so that we didn't fall of) and we made sure that the area was clear of people before dropping the parachutes so that they didn't fall on somebody's head or trip somebody up.

The equipment that we will use to do this experiment is:

2 black binliners

280cm string

5g plasticine

Scissors

Sellotape

Meter ruler

Stopwatch

Prediction

I predict that when we do the experiment that the bigger the surface area of the parachute the longer the parachute will take to reach the ground. I think this because the bigger the surface area the bigger the air resistance. The bigger the air resistance the quicker the terminal speed is reached. The quicker the terminal speed is reached the slower the terminal speed is. The slower the terminal speed is the slower the decent.

Terminal speed is when the force acting down on an object (in this case gravity) is equal to the forse acting up on an object (in this case air resistance). As been as the terminal speed is what speed an object is falling down at and all through an objects decent it is speeding up (untill it reaches it's terminal speed), the quicker the terminal speed is reached, the slower the object will desend.

Table Of Results

Meathod

. Collect all materials

2. Make parachutes

3. Drop parachutes 4 times each and time how long it takes for them to get to reach the ground

The meathod that I used to carry out the experiment is explained in more detail in the plan (above).

Diagram

Conclusion

My graph shows that the bigger the the surface area of the parachute was, the longer it took to reach the ground. You can see this because when I drew my graph there was a curve of best fit. Because it was a curve of best fit and not a line it tells me that as well as the time increasing as the area increases, that the difference in the time it took for the parachute to decend was decreasing. This must mean that as the areas got bigger the time it took for the parachute to reach the ground was evening out.

I think that the graph showed that as the surface area got bigger the time the parachute took to reach the ground increased because as the surface area got bigger so did the air resistance and as the air resistance got bigger it equaled the pressure pushing down on it (gravity). When the air resistance equaled the force of gravity, the falling object had no resultant force. Having no resultant force means that the object will not speed up any further during its decent (Newton's 1'st law: A mass has no resultant force if it is moving and keeps moving at a constant speed in a straight line). So the quicker the point of no resultant force is reached the slower the resultant force is because a mass is speeding up all the time that it is decending (untill it has no resultant force). I think that the curve of best fit went the way it did because there has to be a point at which the point of no resultant force can be reached no quicker. The curve occured because the parachutes were getting towards that point.

Evaluation

When I did this experiment the method that I used worked well and I didn't have to do anything other than what was written in my plan.

I think that our results are quite accurate, we tried to ensure that they are accurate by timing each parachute 4 times and then taking an average this helps to make the results accurate because when an average is taken it is supposed tocancl out any little timing errors made, the more times the average is taken from the more accurate it will be. We also did everything the same so that the experiment was a fair test e.g. using the same weight of plasticine on each parachute, exactly what we did to make it a fair test is explaind fully in the plan.

When I got my results there were 3 anomalous results one at 100cm , one at 225cm and one at 1225cm . An anomalous result is when a result doesn't fit in with the rest of the results, the two results that I have listed above don't fit onto my curve of best fit. I think we got these anomalous results because of human error, are reaction times could have been slowed when timing the results or the parachutes could have been faulty or measured slightly wrongly. There are lots of reasons for human error.

If I did the experiment again I could improve it by dropping each parachute more than 4 times so that the results were more accurate. I could use a better material than black bags to make the parachutes out of because then they wouldn't ruccle when sellotape was put on them or rip when you are trying to cut them out.

I could extend my investigation by carrying on an using bigger surface areas. If I did do this I think that eventually the line on the graph would straighten off because eventually the parachutes wouldn't be able to reach the point of no resultant force any quicker.