物理题（Physics problem）.doc

物理题（Physics problem） The sixteenth national junior high school application physics knowledge competition examination questions First, select the four option problem following each question there are only one is correct, the correct option in front of the letters in the brackets after the title (3 points per day, a total of 15 points) 1., Xiao Liang from the supermarket to buy a glass bottle of tin covered cans, want to open the bottle, but how can not screw. Little bright brother gently screwdriver along the edge of the bottle a few times, a twist on the open. This is mainly because the screwdriver can be used to pry the bottle cap into place The increase of A. cap diameter, reducing the pressure on the side wall of the bottle B. reduces the contact area between the bottle cap and the bottle mouth C. reduces the pressure difference between the inside and outside gases of the vial D. increased the pressure on the other side of the lid by prying the side of the lid 2. the top of the tower of a high voltage transmission line has one (or two) thinner wire than the following transmission line (as shown in Figure 1 to figure 2), and its function is [.] A. to strengthen the stability of the tower, B transmission of zero line current C. lightning protection plays the role of lightning rod The D. is used as backup line for emergency use when the transmission line is disconnected 3. when you take a picture with an ordinary camera, focus the camera on the distance from the camera lens. It is not very convenient to use. There is a fool camera, as long as all the pictures you want to take into the viewfinder, whether distant or near objects, in the photos are relatively clear, so that the process of photography has become very fast. The dumb camera doesnt need to focus A. uses a telephoto lens that makes the near and distant objects imaged differently B uses a short focal length lens to make the near and distant objects imaged differently C. uses a telephoto lens that allows dif