The backspin was used to ensure contact with the dam underwater.
If they imparted forward spin on the bomb it would hit the dam and shoot skyward when it hit, just like if you rolled a bicyle tire at the curb, it wants to keep going.
Wallace reasoned that in order to get the bomb to counteract the forward velocity of the aircraft, the bomb would have to be spun backwards at a rapid velocity during flight. He also reasoned that would have to calculate (using the drop distance from the dam, the forward velocity of the aircraft, and the elevation of the aircraft), how many bounces the bomb would achieve on the water before reaching the dam, and on each bounce, how much drag the bomb would incur as it scooped through the water on each bounce. Using these specific factors in his calculations, he was able to fix the velocity of backspinning required (almost 600 revolutions per minute) to enable the bomb to slow down on each bounce to the point that the bomb would almost be at zero velocity at the point that the last contact with the water was made- occurring right adjacent to the dam.
As the original author of this answer correctly pointed out, the backspin then guaranteed that, if it had any forward velocity left at all, the bomb would then simply contact the dam face, roll down the wall face of the dam to a depth of 30 feet where an internal pneumatic pistol ignited the charge causing the bomb to explode hard against the dam surface.
Although the backspin would allow the cylindrical bombs to "crawl" down the dam face if they came to rest exactly at its surface, there is evidence that Wallace also chose back spin to take advantage of a more subtle aspect of physics - Kutta's lift theorem. More commonly known as the Magnus effect, Kutta's theorem explains the unmistakable curving trajectory of a spinning Baseball. Given the operational uncertainties of the attack - night time, altitude variations, crude aiming devices and monumental distractions - Wallace had to appreciate the fact that most bombs would likely strike the surface of the dam on the lake side, bounce off, and sink some distance away. Archival footage of the Royal Navy version of the weapon actually shows these bombs bouncing off the side of a ship. Once the heavy, spinning bomb begins to sink, however, the upward flow of water around the cylinder, coupled with the back rotation, generates a truly impressive hydrodynamic force pulling the bomb back toward the target - the Magnus effect. In the end, the bomb needed to be spun in order to stabilize its path to the target and to prevent it from tumbling out of control. There was no alternative. Sir Barnes Wallace, through his meticulous experiments and his understanding of physics, was able to select the direction of spin that would maximize the bomb's effects.
the US decide to drop two atomic bombs on Japan, not china
their nose
by serra
to train
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Wallace and Gromit are out of cheese and decide to build a rocket to go to the moon which is made of cheese .
Mr. Murray doesn't grab Charles as they tesser away from IT because with Mr. Murray pulling on him and IT also pulling on him, it could have resulted in death or serious brain injury for Charles Wallace.
You're going about it backwards, I'm afraid -- the title comes from what you've written, not first! Finish your story and then decide if that's a good title.
Stacey decided to take the money he earned from selling the hogs to visit her brother in university.
Dylan wanted to attack the play because he felt the main character's dog was portrayed unfairly as the villain, reflecting his own experiences of feeling misunderstood and unfairly judged by others. He believed the play lacked depth and realistic character development, and he wanted to challenge the school's typical approach to theater productions.
LAKE AFAR on floors 5 - 11,i suggest you buy the time & darkness strategey book from gamestop or barnes & noble just in case you decide 2 start your game over..veronica
I couldn't decide what to wear to the party.My boss asked me to decide which office I wanted.The patient had to decide whether or not to have minor surgery.
will decide or going to decide or decidingor will have decided.Examples:I will decide about the party tomorrow.I am going to decide about the party tomorrow.I am deciding about the party tomorrow.I will have decided about tomorrow's party by tonight.
Decide is a verb.
they decide price and quantity.
He had to decide what to do next. The group was not able to decide which direction they should go.
Decide is a verb. You decide what you want to do today.