A lever of length 9cm has its load arm 5cm long and the effort arm 9cm long:
(a) Which class does the lever belong to?
(b) What will be the mechanical advantage and velocity ratio if the efficiency becomes 50%?
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Solution
Given:
Length of lever = 9 cm; Load arm = 5 cm; Effort arm = 9 cm.
(a)∵ Effort arm > Load arm and Effort arm = Length of arm ∴ Fulcrum is at one end, the effort is at another end and load is in between.
⇒ It is a class II lever.
(b) For an ideal lever :
Mechanical advantage, MA=Effort armLoad arm=95 MA=1.8
And, velocity ratio, VR=velocity of effort pointvelocity of load point =Effort armLoad arm=1.8
But for a real lever with the efficiency of 50%, MA′=η×VR=0.5×1.8 MA′=0.9 VR remains the same (VR =1.8) as the lever is rigid and does not vary with efficiency.