In what situation you will get less wet getting to the car
It is raining, but you need to get to your car, which stands at the farthest end of the parking lot.
Will you run to it or not, if your goal is to get wet as little as possible? How will you behave if you have an umbrella?
In order to answer this question, you need to reconcile two contradictory facts that affect the way of your thinking. Here are the arguments for running: the longer you are in the rain, the more raindrops fall on your head, and the more you get wet. If you run, you will reduce the time of being in the rain and thereby remain drier.
However, there is also an argument against running. With horizontal movement, you will face those raindrops that you would not face in case you remain on the spot. A person who runs in the rain gets wetter than the one who just stands under the rain.
This is a remarkable argument, but it is simply not applicable in this case. You need to get to your car anyway. Imagine that you are racing through the parking lot at infinite speed. Your feelings are also infinitely aggravated, and therefore you do not bump into other cars. Time seems to have stopped for you. It is similar to tp the effect of slow motion. Raindrops do not seem to move and they stay in the air. During this rapid run, not a single drop will fall on your head or back. However, in order to reach your car, you need to “breakthrough” a kind of rain tunnel. Therefore, part of your clothes in front absorb every drop that is on the way from shelter to the car.
When you move with a normal speed, you will definitely face those raindrops. The number of raindrops depends on your level track length and the time you need to overcome this distance. The trip length in this task is a set condition. The only thing you can control is the move time. In order to stay maximally dry, you need to run as fast as possible. Run will lead to the fact that you will be less wet, of course, if you do not have an umbrella.
Most umbrellas are big enough to not let a person become wet. However, as you know, many things are different in practice.
Umbrellas create barriers for rain and create a raindrop-free zone. With a vertical drop of raindrops and an umbrella in the form of a circle, the raindrop-free zone is similar to a cylinder. If the rain falls at an angle, the raindrop-free zone becomes a sloping cylinder. Consequently, it is better to tilt the umbrella in the direction of the falling rain. This will result in the raindrop-free zone becoming the correct cylinder again.
Standing human body does not fit into the inclined cylinder. If the rain is accompanied by a hurricane wind that directs raindrops horizontally at you, you have to hold an umbrella horizontally. An umbrella with a diameter of three feet will protect only half of your body. The second half will get wet.
You will get wetter from the wind and the movement. You need to tilt the umbrella forward in the direction of your movement to provide maximum protection. In fact, even if the umbrella occupies the optimum position, the wind and the movement of a person will still negate everything. Running at a speed of 10 miles/hour without wind with vertical rain will require the same inclination as standing in the rain at a wind of 10 miles/hour. Anyway, additionally to its normal falling speed, raindrops will hit you horizontally, at a speed of 10 miles/hour.
Within the vertical rain, the best option is to walk slowly. You will not need to tilt an umbrella much and you will stay dry. Ideally, you need to move so fast that your legs do not end up outside this zone. This way, you will remain dry.
Surely, everything is much more complicated in real life. The rain falling on an umbrella does not evaporate. Drops flow and fall down on the same surface of the cylinder created by your umbrella. It means that any part of your body that goes out this raindrop-free zone will get wet faster than if you walked without an umbrella.