So far, however, all searches have come up empty. Because different theories predict different fifth force properties, he says, physicists have looked for its subtle effects in everything from surveys of astronomical objects like galaxies to the miniscule motions of custom-built microscopic instruments. “This work of ‘fifth force’ searches actually goes on over the entire length scale of human observation,” says NIST physicist Benjamin Heacock, the study’s lead author. Published in Science in September, the study also includes measurements of the precise structure of both silicon crystals and neutrons themselves. An international collaboration of researchers used neutrons and a silicon crystal to set new limits on the strength of a potential fifth fundamental force at atomic scales. Now, a recent experiment carried out at the National Institute of Standards and Technology (NIST) is offering fresh hints about a fifth force’s possible character. The discovery of such a force could potentially resolve some of the biggest open questions in physics today, from the nature of dark energy to the seemingly irreconcilable differences between quantum mechanics and general relativity. Yet that has not stopped them from ardently searching for an additional, as-yet-unknown fifth fundamental force. If you have any queries regarding Friction CBSE Class 8 Science MCQs Multiple Choice Questions with Answers, drop a comment below and we will get back to you soon.Mysterious forces may be a reliable trope in science fiction, but in reality, physicists have long agreed that all interactions between objects evidently arise from just four fundamental forces.
Force physics science questions with pictures pdf#
We hope the given NCERT MCQ Questions for Class 8 Science Chapter 12 Friction with Answers Pdf free download will help you.
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Friction can be reduced by using ball bearings in some machines. Friction is independent of the nature of surfaces in contact. Friction can be reduced by using lubricants. It is easier to move a heavy object than a light object. Friction decreases with increase in the smoothness of the surface. Sliding friction is less than rolling friction. Friction is dependent on area of contact. Friction always works in opposite direction to the relative motion. A soapy floor is slippery due to increased friction. State whether the given statements are true or false.ġ. The sole of shoes and the tyres of vehicles are treaded to _ friction. _ force is responsible for downward movement of a parachutist when he jumps from an aircraft Answerġ4. Static friction comes into play when we try to move an object at _. Friction depends on the _ of substances in contact. In many machines, friction is reduced by using _. Rough surfaces produce _ friction than smooth surfaces. All objects moving in fluids have _ shape to reduce _. Rolling friction is _ than sliding and static friction. Friction can be increased by making surface _. Sliding friction is _ than static friction. Match the items given in column I suitably with those given in column II. The sole of the shoes becomes plain after wearing it for several months. Why?Īnswer: (b) To reduce the friction of fluid Choose the correct arrangement.Ī boat or an aeroplane has a pointed or tapering front / head. The frictional force exerted by fluids is also called _įour children were asked to arrange forces due to rolling, static and sliding frictions in an increasing order. Sliding friction is _ than / to rolling friction Spring balance is a device used for measuring the _ acting on an object.Ī matchstick struck on a matchbox catches fire easily because (d) Force of friction is very less AnswerĪnswer: (d) Force of friction is very less It is difficult to walk on an oily floor because Which of the following is responsible for wearing out of bicycle tyres? If we apply oil on door hinges, the friction will Which of the following is not a smooth surface?Ī toy car released with the same initial speed will travel farthest on To sharpen the blade of a knife by rubbing it against a surface, which of the following will be most suitable? AnswerĪnswer: (d) irrespective of whether the objects are solid, liquid or gaseous. (d) irrespective of whether the objects are solid, liquid or gaseous. (c) only if one of the two objects is gaseous.
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(b) only if one of the two objects is liquid. Whenever the surfaces in contact tend to move or move with respect to each other, the force of friction comes into play Which of the following produces least friction?