Contents

Force and Machine       (old version text book)       


1) Friction: Friction is a force which opposes motion.

2) Machine is devices which helps us in doing our work and make our life easier.

3) Causes of friction: All solid materials have some roughness. This roughness causes friction.

4) Mass: 1) Mass is the quantity of matter in an object. 2) Mass remain same everywhere.

5) Weight: 1) The gravitational force acting on an object is called its weight.    2) Weight does not remain the same everywhere.

6) Friction helps us in walking and running.           

7) Friction prevents the vehicle from skidding.      

8) Moving objects slow down due to friction.

9) Friction causes wastage of energy.

10) Gravitational force is the force of attraction that pulls all objects towards the center of the earth.

11) The claw hammer is an example of class lever.

12) The SI unit of force is Newton (N).

13) The unit of Mass is Kg.

14) Lever is one of the simplest types of machine which helps us to do work more easily.

15) Kinds of liver: Liver is classified in to three classes based on relative position of the Fulcrum (F), the Effort (E), and the Load (L).

16) Lever of class I: In first class lever, the fulcrum is between the effort and the load. Examples Scissors, claw hammer and sea saw.


17) Lever of Class II: In the second lever, the load is between the fulcrum and the efforts. Examples Bottle opener, wheelbarrow, etc.


18) Lever of Class III: In third class lever the efforts is between the fulcrum and the load. Examples, Stapler, human arm, fishing rod.


19) Balance forces are equal and opposite in direction.

20) Wedges and inclined planes are simple machines which are frequently used in daily life.


MCQs


Unite of force in SI is………………
a) Meter                                

b) Pound
c) Kilogram                          

d) Newton

d

Ball bearings reduce friction because they……
a) Reduce roughness of surface                      
b) Roll on surface to reduce friction
c) Increase the surface area in contact
d) Heat up the surface area in contact

b

A sharpener is an example of…………………
a) Lever                                

b) Wedge
c) Inclined Plane                 

d) Inertia

b

The quantity of matter present in an object is it’s……………..
a) Density                                             

b) Weight
c) Mass                                 

d) Volume

c