Ann and Bob play on a uniform seesaw. The seesaw is 4m long and Ann and Bob weigh 600N and 800N respectively. If both Ann and Bob start at one end of the seesaw and Bob starts to walk up the seesaw at 2m/s, after how long will the seesaw turn?

(expect a diagram of a uniform seesaw with a pivot in the middle, infered from the question)

For the seesaw to turn, Bob must create a greater Moment than Ann.

Moment = Force * Perpedicular distance to pivot

Ann's Moment = 600N * 2m = 1200Nm

Calculate the point at which the moments are equal:

Bob's Moment = 800N * Xm = 1200Nm

solve to find X = 1.5m.

Therefore Bob must have travelled 3.5m.

Use of Speed = Distance / Time, rearanged to Time = Distance / Speed, to find time, t:

t = 3.5m / 2m/s = 1.75s.