Pennies, dropping

Although acids do not dissoive metals with the ease depicted in movies or television, they do dissolve many metals. A penny dropped in concentrated nitric acid or a small iron nail submerged in hydrochloric acid will dissolve away in several minutes. 

Penny, G. W. Using Electrostatic Forces to Reduce Pres,sure Drop in Fabric Filters. Powder Teclmol. 18 (1977), pp. 111-116. 

For flammable gases the minimum ignition energy is typically 0.1 mJ. The mass of a penny is typically 2.6 g. How far must this penny be dropped to contain the kinetic energy equal to 0.1 mJ ... 

Another variation of this activity is to guess the number of water drops that can be placed on a penny using a medicine dropper. 

Dropping Pennies front the Empire State Building... 

One question Fm repeatedly asked deals with death. New York City, and pennies. Just the other day, Teja from Slovenia asked me If I accidentally drop a penny from the Empire State Building, would it kill someone walking on the street below Would it literally go through the skull and brain and out the bottom of the chin My friend Nina accidentally dropped a penny and has been worried ever since. ... 

Occasionally, some of the topics or puzzles in this book will seem simple or frivolous, including dropping pennies from the Empire State Building or wondering if Jesus could calculate 43 x 31. However, these are questions that fans have often posed to me, and I love some of these quirkies the best. I agree with the Austrian physicist Paul Ehrenfest who said Ask questions. Don t be afraid to appear stupid. The stupid questions are usually the best and hardest to answer. They force the speaker to think about the basic problem. ... 

Feedback will of course be positive as well as negative. But being positive does not necessarily make it any easier to accept. It is not unknown for people to attempt to cling on to a poor self-image in the face of contradictory positive feedback they may need help in getting the penny of success to drop. 

Molecules that are made of few atoms are very small. Molecules are so small that you cannot see one even with the most powerful microscope. One drop of water contains two million quadrillion (2,000,000,000,000,000,000,000) molecules. If you took two million quadrillion pennies and stacked one on top of the other, you would have three hundred thousand (300,000) stacks of pennies. Each stack would reach from the Sun to Pluto. 

When some critical crack length (between 200 pm and 400 pm, i.e. about 15% of the contact diameter) is reached, a brittle propagation stage is observed which is associated with a sudden and drastic drop in the lateral stiffness, K. The measured crack width in the plane of the contact is then of the order of magnitude of the contact diameter. Post-mortem microscope observation of specimen cross sections in the contact zone (Fig. 8) indicates that the depth of the cracks is of the order of magnitude of the contact radius (i.e. about 900 pm). The two deep cracks induced at the edge of the contact may thus be viewed as some kind of half-penny cracks whose radii are approximately equal to the radius of the contact. In the subsequent part of this paper, the two deep cracks will be referred to as primary cracks . 

Figure 6.6 shows a design for a decanter. After the two-phase mixture enters the decanter at the feed nozzle, the liquid jet must be diffused to prevent mixing of the two phases and promote settling of the dispersed phase. One way to accomplish this is to insert two closely spaced, perforated parallel plates across the jet, as shown in Figure 6.6. The first plate drops the pressine of the jet, and the second plate decreases its velocity. Jacobs and Penny [17] recommend that the flow area of the first plate be 3 to 10% of the decanter flow area, and the second plate 20 to 50% of the decanter flow area. Another way to disperse the entering liquid jet, and at the same time enhance coalescence of the dispersed phase, is to use a wire-mesh pad in front of the feed nozzle.

The drop diameter, d, for use in Equation 6.16 is difficult to determine. There is not a single drop size but a distribution of drop sizes. Jacobs and Penny [17] recommend a drop diameter of 150 micrometers, which is conservative and compensates somewhat for the other assun5)tions in Equation 6.16. 

Drop the pennies into the salt solution. Stir and observe. 

Than aro required a pan 2 deep, S wide and Ify long, a number of pieces of blanket 12 iquara whieh muA be wall dampened before using, and a cap drop per made by driving 150 6 penny nails, for one inch of their Wngtii into a wooden block 7 x 9. 11 thick and fitted with a handle as shown in illuAration. The heads o the nails should be well leveled up so that eveq one touches when dropper Aands on a Hat surface. Also cut a lot of pieces of poAer paper 6 x and place them in kwe piles on the work table. They arc for dropping the cape into. The cap composition is made as follows ... 

Drop the penny in the water when you are finished and plunge the burning end of the chopsticks or hot part of the fork into the water as well. 

The surface tension of water allows it to bead up on many surfaces. In this MiniLab, you will compete to see who can deposit the most drops of water and the most drops of an aqueous detergent solution on a penny. 

Fill a microtip pipet with tap water, and count the number of drops you can deposit on the penny before water spills over the edge. Record the number of drops. 

Water The Molecular View Intermolecular Forces in Water Water Physical Properties Revisited More Evidence for Water s Intermolecular Forces MiniLab 13.1 How many drops can you put on a penny ... 

So that the 2-inch holes in the intake manifold (tee) would not ingest a rock big enough to jam them, I drilled several holes to pass a 16-penny nail vertically through each side of the tee to form a rough grate. Why a nail It could be lifted out to release debris and dropped back in— all without the need for tools. To facilitate this, I added a rubber gron> met to the nail to hold the head of it above the tee for easy removal. 

The goal of this activity is to move a penny from the origin and drop it in a cup. 

Have your partner place three cups at different locations on your desk. Place a penny on the origin point (0, 0). Begin with the penny. Your goal is to be able to drop it in each cup, starting from the origin. Do not forget that your first movement might be to raise the penny off the desk, say, 5 inches, or on the z-axis. Use the tape measure to measure the z-axis. 

---