Bob and Sally sit on a 4 m long see-saw that has its fulcrum smack in the center of the board. If 50 kg Sally is sitting at one end of the plank, where should 70 kg Bob sit on the other side relative to the fulcrum so the net Torque is zero?

1.43m

Explanation:

Given data

m1= 50kg

m2=70kg

We are told that Sally m1= 50 sat at one end which is 2m from the center

Hence, the summation of clockwise moment = summation of anticlockwise moment

See the attached image for your reference

50*2= 70*x

100= 70x

x= 100/70

x=1.43m

Hence the mass m2 will be at the 1.43m mark for the net torque to be zero

1 - wave length

2 - amplitude

3 - crest

4 - trough

explanation:

duh.