What is sound ?
Sound is produced by vibrating objects. i) In human beings, the vibration of the vocal cords produces sound.ii) Sound travels through a medium (gas, liquid or solid). It cannot travel in vacuum.
What is fluids ?
The common name of gases and liquids is fluids. So we can say that fluids exert force of friction on objects in motion through them.
What is drag ?
The frictional force exerted by fluids is also called drag.
Explain why objects moving in fluids must have special shapes.
Moving objects in fluid must have special shapes because the drag force or the friction force depends on the object’s shape. Therefore, special shapes are designed to minimize the opposing frictional force. Fluid friction can be minimised by giving suitable shapes to bodies moving in fluids.
What is Friction ?
Friction opposes the relative motion between two surfaces in contact. It acts on both the surfaces.
friction depends on
Friction depends on how hard the two surfaces press together.
Which is smaller – Sliding friction or static friction.
Sliding friction is smaller than static friction.
What is sliding friction ?
Since the rolling friction is smaller than the sliding friction, sliding is replaced in most machines by rolling by the use of ball bearings. Commonexamples are the use of ball bearings between hubs and the axles of ceiling , Rolling reduces friction fans and bicycles
What is rolling friction ?
When one body rolls over the surface of another body, the resistance to its motion is called rolling friction. Rolling reduces friction. It is always easier to roll than to slide a body over another.
What is lubricants ?
The substances which reduce friction are called lubricants.