Question

A crowbar 4 m long has its fulcrum 50 cm from one end. What minimum effort is required to displace a weight of 500 kgf? Calculate the M.A. of the crowbar.

Answer 1

A crowbar is a class I lever, Thus its fulcrum lies in between the load and effort

Given, load, L = 500 kgf

Lenght of crowbar = 4 m = 400cm

Therefore, load arm = 50 cm

Effort arm = 400 - 50 cm = 350 cm 

Let effort = E

Now, M.A = `"effort arm"/"load arm" = 350/50` = 7

Also, M.A = `"L"/"E"`

7 = `500/"E"`

or, E = 71.4 kgf