13. What is a lever?
Ans. A lever is a rigid bar either straight or bent which can turn about a fixed point called the fulcrum.
14. Describe three orders of levers giving an example of each. Draw neat diagrams showing the positions of fulcrum, load and effort in each kind of lever.
Ans. A lever can be of three types that is class 1 lever, class 2 lever and class 3 lever.
Class 1 lever-
*the levers in which the fulcrum is in between the load and the effort are called the levers of class 1. Draw figure 4.7 from your physics book.
*the mechanical advantage of levers of class 1 can be greater than 1, equal to 1 or less than one.
*Example seesaw, a pair of scissors, beam balance, a pair of pliers etc.
Class 2 lever-
*the levers in which the load is in between the pulchrum and the effort are called the levers of class 2. Draw figure 4.9 from your physics book.
*The mechanical advantage of class 2 levers is always more than 1.
*Examples of class two levers are are nutcracker, wheelbarrow, paper cutter, lemon squeezer etc.
Class 3 levers-
*the levers in which the effort is in between the welcome and the load are called the levers of class 3. Draw figure 4.11 from your physics book.
*The mechanical advantage of class 3 levers is always less than 1.
*Examples of class 3 levers are are a pair of tongs, sugar tongs, knife, spade for lifting soil or coal etc.
15.what do you mean by the mechanical advantage of a lever?
Ans.the mechanical advantage of a lever is equal to the ratio of the effort arm to the load arm.
Mechanical advantage= load/effort.
Or
Mechanical advantage=effort arm/load arm.
It gives us an idea that how many times our efforts get multiplied by the machine.
16. Which class of lever has the mechanical advantage always more than one? Give an example.
Ans. Class 2 lever is a example where mechanical advantage is always more than 1.
Example nutcracker, wheelbarrow, bottle opener etc.
17. Which class of lever has the mechanical advantage always less than 1? Give an example.
Ans. Class 3 lever is a lever was mechanical advantage is always less than 1. Example pair of tongs ,knife ,spade used for throwing all lifting soil etc.
18. Give one example of class one lever in each case where the mechanical an is a) more than one. b) equal to 1. C) less than 1.
Ans. A pair of plier is an example of class 1 lever where mechanical advantage is greater than 1.
Beam balance example of class 1 where mechanical advantage is equal to 1.
a pair of scissors age an example of class 1 lever where mechanical advantage is less than n1.
19. Name the class to which the following levers belong:
A. A pair of scissors -class 1 lever
B. Lemon squeezer -class 2 lever
C. A nutcracker - class 2 lever
D. A pair of sugar tongs-class 3 lever
E. a beam balance - class 1 lever
F. An oar roaming about- class 1 lever
G. a wheelbarrow - class2 lever.
H. A seesaw-class 1 lever
I. A pair of pliers-class 1 lever
J. Crowbar- class 1 lever
20 the diagram given below shows the three kinds of levers. Name the class of each lever and give one example of each class.
Ans. a) class 2 lever. Example wheelbarrow bottle opener etc.
b) class 1 lever. Example beam balance, seesaw etc.
C) class 3 lever. Speed using for throwing soil, sugar tong etc.
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