Classical Physics

Hi, I'm trying to find the area of a parachute cloth required for a landing. I should specify that it is not homework. Consider a person of mass m. Let the time required to come down to the surface safely be t. Let the height of the parachute be h. Then, h=1/2at^2, a=acceleration during the landing. As there will be much drag, using Newton's Second Law - Net force=Weight -Drag ma=mg-1/2dv^2CA Here, d=density of air, v=velocity of the parachute, C=drag coefficient and A=area of the parachute. So, it comes that - a=g-(dv^2CA)/2m Substituting the value of a in the first equation - h=1/2[g-(dv^2CA)/2m]t^2 Now to calculate the area required. The question is: I…

Solar panels exploit photonic momentum to propel objects. If instead of a plain "sail" we place a solar panel (that harvests light for electric power) would that reduce the efficiency of the propelling action? If so by how much?

Hello All I have a question about the cold touch of the glass versus the warm touch of the plastic. As we know it is not because of the heat conductivity as glass has very low heat conductivity. It is speculated that the difference is because of heat capacity of glass. Glass has higher heat capacity than PC and acrylic and so it has the colder touch, but how about when you compare it with a plastic such as PP. base on the literature, PP has higher heat capacity than glass but it does not hace a cold touch. so, what are the main reason for the cold touch of glass? if we want to have a plastic to have the same cold touch, what parameters or properties of the pla…

Must a core for a 100mH/10A inductor have a larger cross section than a 100mH/1A inductor? I am confused here. Ampere's law says that the Field strength is proportional to the current flowing though the windings (H= n.I/lm). Core saturation B/H (permeability, μ in fact) at the other hand does not depend on the actual core area. One may logically conclude that a 10A inductor could be assembled with the exact same core, at least if one would be able to fit the thicker wire. This seems counter-intuitive to me.

Hello everyone. Even simple situations can be not so easy to deal with. I ask myself a simple question and I haven't found an easy explanation. Imagine a plane taking off from the north pole, and flying at 1000 km/h to the equator. When it arrives there it turns "right", in direction of the west, that is in the opposite direction of earth rotation (it is still flying at same proper speed of 1000 km/h). The plane doesn't land during that time. The very simple question is : what will be its speed relatively to the ground ? At north pole it will have no angular momentum due to earth rotation, because it is located at the axis of earth sphere. Its speed relative…

Would an audibly vibrating piece of metal (i.e. a tuning fork) behave in the same way as it was reduced in size (extremely small)? presumably if you blast relatively lower frequency soundwaves at it, you could get it to vibrate harmonically, but how does scale change things?

Can anybody give the values of the three constants used in the Steinhart-Hart equation ?

Hello, I'm new here. Can anyone check these equations if they are correct. Rolling velocity Without friction - v=gt sin x With friction - v=gt(sin x- ucos x) x is angle of inclination and u is frictional coefficient and t is time taken and g is acceleration due to gravity.

Putting a simple electrochemical cell, except for the introduction of the depolarizer. The NaCl solution is placed two electrode potential difference. For a fixed load of the external circuit of the discharge element approximately 10-15%. After discharge element, without opening an external circuit element will cover a glass bulb and increase the percentage of carbon dioxide up to 3% in the composition of air under the bulb - we can fix the charge element Keeping a stable amount of carbon dioxide under the bulb - can maintain the health of the element.

Can someone explain to me why according to physics we can never really touch anything? I'm talking about "touch" as in the sense.

Lets say i am falling from a great height, and i am wearing a bag that is the same mass as me, and just before i hit the ground i throw the bag at the ground at a velocity (w.r.t. the ground) twice that which i am falling relative to the ground. Would i survive?

I'm having a bit of a mental block with integrating a trig function that's cropped up in some work I'm doing on acoustics. The bones of it are dr/dt=(simple terms)-(A-Bcos{wt))^2/(C+Dsin(wt)) A, B, C, D and w all constant. Pointers yo a way forward would be much appreciated Seth

If i was in a tube of circular cross section that curved on itself (doughnut shaped), and i was in space floating in the center if the tube and the tube was spinning very fast, negating all the effects of real gravity and air inside the tube, would i be attracted to any particular side of the tube??? Follow up question, is it correct to say that i have to be touching the sides of the spinning tube in order to feel the effects of artificial gravity

I have an experiment to transfer solar energy to mechanical energy. First of all is a cone inspired by an axis. On the cone are two tiny cups of water. The whole system is put close to the glass in the room to get sunlight and avoid affection of wind Then, there will be interaction between sunlight and water molecules, which makes the cone rotate It is better to implement this idea in tropical countries, where there is plenty of sunlight and temperature is so high, which can heat the water cups See my clip for more detail link removed

Hi. I just made an animation of Aberration (aka tilting of the telescope) in the Michelson Morley experiment. The aim of the animation is to illustrate these quotes: -- Michelson, 1887 paper. Any comments?

I had an idea for a way to make orbital transfers without using fuel and I'd like an expert to pitch in: link removed How feasible would it be? How precisely can we predict the motion of a spacecraft over millions of kilometers? edit: since the link was removed, I'll quote it here:

Hi, trying to determine the forces acting upon this mechanical system, Pics attached. The mechanical device works in a similar fashion to a crankshaft and piston. the crankshaft contains 2 gears, 1 on the crank journal which is fixed to a lever that runs along a track on a roller, the second gear is the sun gear that's in the center of the crank, this gear is not fixed to the crank, and runs through the crankshafts central axle, "a double axle". Fig 1 split crank image. shows a simple view of the system. Fig 3-4, 3D image of system. both crankshaft systems are the same, they are placed 180 degrees apart opposite each other e.g. a flat 2 cylinder engine. the gears ha…

Is wind actually the feeling of clusters of electrons passing through the magnetic field?

As i was told in another post that certain things didnt exist because of my context of words i have chosen to repost differently and hope that he can clearly understand me, to see if i could get an opinion on the subject. My first question is regarding radio towers. I know that objects can be moved with radio technology, not only to be used for communication. So, this leads me to ask if a radio tower that drew it's source of energy from the earth or a geologically strategic point could this have serious consequences. For example, if it was used not only by commercial entities to provide services such as wifi,television, and data usage.....could it deplete an area of this…

I was wondering if there are cases in which momentum or energy are not both conserved together ie energy conserved, but momentum is not. The source of my confusion stems from the explanation that momentum is conserved in a "closed system" (no matter exchange, no external forces) while energy is conserved in an "isolated system" (no mass or energy exchange with environment).

Back in grade school, I remember learning about some property substances have that requires a certain amount of kinetic energy to increase that object's temperature by a certain number of degrees. For example, a tire iron that's been baking in the sun all day will probably be too hot to pick up with your bear hands. However, an object that has rubber or wood as a handle (such as a shovel) can still be picked up, even though it's been absorbing just as much sunlight as the tire iron. This is because iron has a much smaller _____________________ than wood does: It takes a less kinetic energy to increase iron's temperature than wood. What is this property called? Ca…

If we would live in a Universe where absolute zero is achievable in principle, how would perpetuum mobile that exploits this effect practically look like? Just curious. Which components would it require and how would it function?

Some surfaces like Chrome, car paints etc won't scratch from things like tissue, microfiber cloths etc after dozens of wipes across the surface. But I was thinking about how hard rocks get worn down by water over time or how concrete steps get damaged by soft shoes. So my guess is even the softest cloth will eventually scratch the chrome finish & this seems to be the case as some of my chrome surfaces like on car or indoor appliances only come into contact with soft cloths when cleaning dust, yet they have faint scratches on them. My thinking at first was if it can't create a visable scratch the first few times, it won't ever. Maybe it's like saving 1cent/day & a…

Dear all I have used a bulb which is filled in with water, it works like a convex lens to concentrate solar energy. The performance of the water bulb gets highest level when I incline the bulb like in the clip. Solar light beam focus on a bigger dot, in compared with the dot when let the bulb standing vertically. See my clip at https://www.youtube.com/watch?v=f0Nvc6Q_Ulw