I have the question " A plank is set up and the balanced is zeroed. When the student lies on the plank the reading on the balance is 600N. The balance is 1.75m from the students's feet and the centre of gravity of the student is 1.25 m from their feet. Calculate what is the students mass ? "
I know that W = mg, where W is the weight, m is the mass and g is the value of gravity.
Therefore m = W/g = 600N / 9.81 N
Which equals m = 61.16 N.
Is this correct ?
You have not used the length of the plank and the location of the student's cg. You need to balance the torques around the foot end of the plank.