Friction (part-2)

FRICTION

Q.3. Suppose your writing desk is tilted a little. A book kept on it starts sliding down. Show the direction of frictional force acting on it.
Ans.3.
                               

Q.4. What is the cause of friction?
Ans.4. Friction occurs due to the interlocking of irregularities between two surfaces in motion to each other.

Every object has some sort of irregularities in its surface, so when two surfaces come in contact with each other and one object moves over the another, so their irregularities get interlocked and moving object starts losing its energy in breaking the interlocking and finally it comes to rest.
                                           

Q.5. What are the factors on which friction depends?
Ans.5. There are two factors affecting friction:

1.     Nature of the surfaces: Friction increases with roughness and decreases with smoothness of the surfaces. On rough surfaces, there are a larger number of irregularities than the smooth surfaces resulting in more interlocking and hence more friction than smooth surfaces.

2.     Weight of the object: Friction will increase if the two surfaces are pressed harder. The interlocking between two surfaces becomes more deeper and stronger with increase in weight of the object, hence Friction increases with increase in weight of the object.

Popular posts from this blog

Friction (part-1)

FRICTION Q.1. What is force? Write few of its characteristics. Ans.1.  A push or a pull on an object is called a force.                      Force is a vector quantity (having magnitude  as well as direction).           S.I. unit of Force is N (Newton).           Force can Change the State of Motion.                   Force can Change the Shape of an Object. s          Q.2. What is friction ?      Ans.2.  The force which opposes the motion of an object on the surface of another object is called force of friction. Force of friction is a contact force. The force of friction always opposes the applied force (direction of motion).  
Read more

Sound (part -1) class 8

SOUND Q.1. What is sound? Ans. Sound is a form of energy, a sensation felt by our ears and makes us able to hear something. We hear many sounds around us like: sounds of talking, chirping of birds, ringing of bell, fluttering of clothes, machines etc. Q.2. What is the cause of sound? Ans. Vibration in an object produces sound. To and fro or back and forth motion of an object is called vibration. The energy required to make an object vibrate and produce sound is provided by some outside sources (like our hands, wind etc.). For example: We can feel vibrations by keeping our hand on our throat while speaking where vocal cords vibrate to produce sound. The sound of a ‘Dholak or tabla’ is produced by the vibrations of its stretched membrane on strucking. Q.3. Tabulate the Musical Instruments and their Vibrating Parts which vibrate to produce sound. Ans. S.No. Vibrating Part of Instrument Producing Sound Examples 1. Stretc...
Read more