Question

a diver of mass 60kg stands on the end of a diving board of mass 30kg and length 2m. calculate the force exerted by the spring 30 cm away from the pivot.

(i think that the force asked is 300N since W=mg (30×10))

hence, calculate the upward reaction force at the pivot and state the principle you are using.

(300N wouldnt make the system in equilibrium so i cant use the principle of moments)

Answer 1

I guess it goes (you do not tell me)
spring x = 0, S down
Pivot at x = 0.30, P up
Board wt of 30*10 = 300 N at x = 1 down
Diver wt of 60*10 = 600 N at x = 2 down

P = S + 900

moments about x = 0
.3 P = 300*1 + 600*2
.3 P = 1500
P = 15000/3 = 5,000 N

S = P - 900 = 600 N