Physics forces question

A block of concrete, mass 100kg, lies on a 2m long plank of wood at d= 0.5 from one end.
If a builder lifts up the other end of the plank, how much force must he apply to lift the block?

A) 125 N
B) 12.5 N
C) 250 N
D) 25N
E) 2.5 N


could you tell me the answer? thanks!

The answer is C 250 N

calculate the weight of the block to see the gravitational force on it:
W = 100 kg * 9.81 m/s² (standard gravitational acceleration)
the distance is given as d=0.5m
calculate the toruqe which is
distance* force
981N*0.5m= 450.5N
to uplift the block the builder should apply force by the end of the plank
Force builder= torque/ distance
450.5/2meters= 245 N
you can approximate it into 250
most probably if you use grav as 10 m/s2 you will get around 250
hope this helps