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# dos the size of a parachute matter ? Answered

I'm doing a science fair project on parachutes and need advice

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To answer this question experimentally, I suppose you need some parachutes of different sizes, and some weighty things to attach to the parachutes, and some space somewhere to do some test drops.

Another thing you need is some method for measuring the speed, or kinetic energy, of the dropped object, right before it hits the ground.

Moreover, it would be convenient if you had some method for this that was inexpensive.

One sort of crude way to measure impact energy is with a deformable material like soft clay. The assumption is that depth the object penetrates, is proportional to the kinetic energy of the impact. Historically, this method was used by (maybe invented by?) a Dutch experimenter named Willem Gravesand. He dropped brass balls into soft clay, and published the results from these experiments in 1722.

https://en.wikipedia.org/wiki/Willem_%27s_Gravesan...

I found a modern experimenter, and physics teacher, named Paul Doherty, who has created a slightly more modern version of this experiment, here:

http://www.exo.net/~pauld/workshops/Energy/Kinetic...

This method of measuring the depth of an impact hole, this is essentially a method for measuring kinetic energy. A measurement just as good would be to measure the speed of the falling object.

The usual methods for measuring speed rely on the measurement of time. The way that works is you have known distance interval, L, and you measure the time t it takes for the object to move across that distance. Then the average speed of the object, in that interval of distance or time, is just

v = L/t

If you have a stop watch, that might be good enough. Or another way, is if you have video of the falling object, you can extract time information by analyzing the video; i.e. counting the number of frames, and knowing how much time has elapsed from one frame to the next.

Depends on the weight you cattying. But yes changing the shape and size effects how it works.