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ICSE Class 10 Physics Question 4 of 19

Machines — Question 11

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Question 11

Ramesh went for fishing with his fishing rod. Identify the class of lever for a fishing rod. If a fish exerts a load of 10 N and the distance between fulcrum and fish is 1.5 m, and the effort applied is 0.5 m from the fulcrum, what is the force required by the fisher to pull the fish?

Answer

A fishing rod is an example of a Class III lever.

Here,

  • Fulcrum : at the handle (where the rod pivots)

  • Effort : applied by the fisher's hand along the rod

  • Load : the fish at the end of the rod

In Class III levers : Fulcrum — Effort — Load

The principle of moments states that —

Moment of the load about the fulcrum = Moment of the effort about the fulcrum

∴ Effort × Effort Arm = Load × Load Arm .......... (i)

Given :

Load (L) = 10 N

Load arm (distance between fulcrum and fish) = 1.5 m

Effort arm (distance between fulcrum and applied effort) = 0.5 m

From (i)

Effort x 0.5 = 10 x 1.5

⇒ Effort = 150.5\dfrac{15}{0.5} = 30 N