Question 16 to 20

Q.16. Write down a relation expressing the mechanical advantage of a lever.
is the relation expressing the mechanical advantage of a lever.

Q.17. Name the three classes of levers and state how are they distinguished. Give two examples of each class.
Ans.
The three classes of levers are:
(i) Class I levers: In these types of levers, the fulcrum F is in between the effort E and the load L. Example: a seesaw, a pair of scissors, crowbar.
(ii) Class II levers: In these types of levers, the load L is in between the effort E and the fulcrum F. The effort arm is thus always longer than the load arm. Example: a nut cracker, a bottle opener.
(iii) Class III levers: In these types of levers, the effort E is in between the fulcrum F and the load L and the effort arm is always smaller than the load arm. Example: sugar tongs, forearm used for lifting a load.

Q.18. Give one example each of a class one lever where mechanical advantage is (a) more than 1, and (b) less than 1.
Ans.
(a) More than one: shears used for cutting the thin metal sheets.
(b)Less than one: a pair of scissors whose blades are longer than its handles.

Q.19. What is the use of the lever if its mechanical advantage is (a) more than 1, (b) equal to 1, and (c) less than 1.
Ans.
When mechanical advantage is more than 1, it serves as a force multiplier.
When mechanical advantage is equal to 1, it can be used as a physical balance.
When mechanical advantage is less than 1, it serves to obtain gain in speed.

Q.20. Both a pair of seasors and a pair of plairs belong to the same class of levers. Name the class of lever. Which one has the mechanical advantage less then 1 ?
Ans.
A pair of scissors and a pair of pliers both belong to class I lever.
A pair of scissors has mechanical advantage less than 1.

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