Class Notes NCERT Solutions for CBSE Students
Friction 8th Science – Question: What is a spring balance? How does it work?
Answer: Spring balance is a device which is used to measure the force acting on a body. It consists of a coil spring, which is attached to pointer and scale. When some object is hunt with it the spring stretches and pointer points to the graduated scale to give the measurement of the force.
Question: We have two packets, one is wrapped in jute and other is wrapped in polythene. Which one will be easy to drag and why?
Answer: The packet wrapped in a polythene will be easy to be dragged. Polythene has a smooth surface. It has less irregularities on its surface and so it gets lesser interlocking with other surface thus requiring lesser force to drag it. Jute has coarse surface so it needs more power to drag it.
Question: Why is it easy to drag the sheet from the bed, but it is hard to drag it when quilts are present on it?
Answer: When we drag the sheet from the bed, frictional force comes in play. In the case of a plain sheet it is easy to drag due to less friction. But friction increases when two surfaces are pressed hard against each other, as in the case of quilts on the sheet. Quilts press the sheet hard on the bed and friction increases, so it becomes hard to drag the sheet.
Question: It is easy to move an object on a sliding surface than the plane surface. Why?
Answer: Every surface has some irregularities on it. On a plane surface these irregularities get interlocked easily and it becomes a little hard for the object to move. In case of sliding surfaces, the irregularities do not get enough time to interlock, so the object moves easily on the sliding surface.
Friction 8th Science – Question: Which friction is less static friction or sliding friction? Why?
Answer: Sliding friction is lesser than static friction, because in sliding friction the relative motion between two surfaces is less opposed by friction as the irregularities of the two surfaces in contact do not get enough time to interlock with each other which makes the motion easy.
Question: What would happen, if the floor we walk on, does not produce any friction?
Answer: If there is no friction on the floor, we would not be able to walk on the floor, because it is friction which enables us to stand or walk on the surface. The grooves of our feet or shoes get locked into the irregularities of the floor and makes us stand.
