An object is placed 10 cm from a concave spherical mirror whose radius of curvature is 12 cm.The distance of the image from the mirror is?
Here (u) distance of object from mirror= -10Focal length= -(1/2 of radius of curvature)= -(1/2* 12) =-6So by mirror formula we get,1/F=1/V+1/U-1/6=1/V-1/101/V=1/10–1/61/V=3/30 -5/301/V= -2/30V= -15DISTANCE OF IMAGE FROM MIRROR IS 15 cm left side of mirror
Why do woodworkers recommend owning a drill press?
Because whenever you need to drill a hole, it needs to be perfectly straight. Either up and down, perpendicular to the surface or straight into end grain.Dowels being used as connecting pins need to mate properly with the opposing hole, and won’t unless the hole is perfectly perpendicular to the surface.Drilling shelf pins is another reason, although that can also be accomplished with a jig and a cordless drill.It’s not just regular twist bits either to think of.Forstner bits are used for drilling the holes needed for modern door hinges. Again, if that’s not perfectly perpendicular to the surface, your hinges and therefore your cabinet doors will be all wonky.There’s also circle cut-out jigs that can only be used with drill presses. Handy for cutting out circles smaller than 6″ diameter.I think there’s many dozens of other uses, but I’ll let someone else have a stab at listing them. Door hinges and shelf-pin holes are the two big ones if you’re doing kitchen cabinetry.
You have 2 balls with identical diameter and weight. One is solid, one is hollow. You can't tell by knocking on them. How can you find the solid one?
Identical in diameter and weight?If they’re the same dimensions, and weigh the same, yet one is hollow, and another isn’t, I can only assume they’re made of different materials. I might be wrong, but I don’t think that two things can be the same dimensions and weight, without also being the same material.So the ball made up of the more-dense material is the hollow one. (because the less dense material has to be full to equal the weight of the more dense one, which requires less material)But, I can think of some other things to try if you can’t discern the material:Drop themI would imagine the hollow one will bounce higher than the solid one. Or maybe it’s the other way around. one of them will bounce higher than the other.(don’t) Put them in waterSame diameter, same weight, but one of them is hollow. So they can’t have the same density, right? Don’t things that are less dense float higher than ones that are more dense?if they both sink to the bottom, then I would look at the rate at which they sink. The one that’s hollow would presumably have air in it, so it would sink more slowly.Maybe experiment with a few different fluids. There’s some sort of name for this principle. For the life of me I forget.User-13466511401027466231 rightly points out that at the same dimensions and weight, they have the same average density. That means they’ll float at the same point in any fluid.Use PhysicsApparently there’s a lot of physicists on Quora that have some fun mathy ways to solve this, too.
What is your favorite gadget of 2018?
Hands down, the Apple Watch 4.Quoted directly from Apple’s website:Series 4 represents a fundamental redesign and re‑engineering of Apple Watch. From the curved corners of the larger, all‑new display to the architecture of the S4 chip, every detail has been thoughtfully considered. Apple Watch has always been a uniquely personal product. And now it’s even more powerful.The display. It’s one of the most elegant looking displays you can find on a smartwatch. It uses a technology on the top of the OLED called LTPO which improves the power efficiency of the device, allowing you to get 18 hours of usage on a single charge despite a smaller battery in a thinner chassis.Digital Crown. This small tiny crown has been made 30 percent smaller than previous generation yet includes 21 more components.ECG feature.This is my favourite feature of the Apple Watch 4. The ECG(Electrocardiogram) feature isn’t just there for kicks and giggles. It actually works as intended and is accurate!S4 chip. A groundbreaking, revolutionary chip with a 64 bit architecture and dual cores, it provides 2x faster performance to it’s predecessor, the S3. Let me show you something.Ok we may not have an Apple Watch benchmark, but holy shit I can do 60fps physically-based Metal rendering and realtime physics on the Series 4