Torque on a diving board with person 3.0m from support

[Drakon25th]

Hello,
Alright, this is the problem:
Calculate the torque about the front support of a diving board exerted by a 70kg person 3.0m from that support
here's the picture:

________________person
|<-1.0m->|<--3.0m-->:

^ ^ ^
| | |
F1 F2 CG
Alright this is what i have done so far:

$$\sum T = 0$$

$$\sum T = m*g*d_F1-F2 - m_p *g*d_F2-person = 0$$

$$\sum T = m*g* 1.0m - 70.kg * g *3.0m = 0$$

$$m*g*1.0m = 70.kg*g*3.0m$$

$$m = (70.kg*g*3.0m)/(g*1.0m)$$

$$m = 210kg$$

I know the answer is supposed to be 2.1 x 10^3 m*N, but i don't know what to do after finding the mass on F1; can someone help me?

 

[ShawnD]

Originally posted by Drakon25th
Calculate the torque about the front support of a diving board exerted by a 70kg person 3.0m from that support

force from gravity:
70 * 9.81 = 686.7N

torque:
686.7 * 3 = 2060.1Nm

 

[Drakon25th]

ooh i see, thank you