4 Three 200N forces are exerted on the beam shown in Fig ure

4. Three 200-N forces are exerted on the beam shown in Fig- ure P7.4. (a) Determine the torques about the axis of ro- tation on the left produced by forces Fl on B and F2on B- (b) At what distance from the axis of rotation must F3 exerted to cause a torque that balances those produced by Fion B and F2 on B on B be

Solution

a)

Torque of F1,

T1 = F1*sin(51)*1

Similarly for F2,

T2 = F2*sin(30)*1.5

So, net torque,

Tnet = F1*sin(51 deg) + F2*sin(30 deg)*1.5 = F1*0.78 + F2*0.75

So, Tnet = 200*0.78 + 200*0.75 = 306 N.m

b)

So, for counteracting torque of F3,

T3 = F3*d = 306

So, d = 306/200 = 1.53 m <-------answer