Question

A 30 kg girl sits on a seesaw 4.0 m from the fulcrum. what distance from the fulcrum should a 40kg boy sit in order to balance the seesaw

Answer 1

The answer is 3m

Step-by-step explanation:

This question has to do with balancing of moment

The moment of force about the fulcrum

Given the mass of the girl =30kg

To force Fg=30*10=300N

Distance of girl from fulcrum l= 4m

Mass of boy 40kg

TO force Fb=40*10=400N

Distance of the boy from fulcrum =?

We know that moment of force about a point M=force*distance

I.e M=f*l

For the boy to cause a balance

His moment must be equal to that of the girls

Therefore

Fg*l=Fb*l

300*4=400*l

1200=400l

L=1200/400

L=3m

Hence the boy must seat 3m away from the fulcrum to balance the seesaw

What is a moment?

A moment is a turning force about a point, The moment is equal to the magnitude of the force multiplied by the perpendicular distance between its line of action and the axis of rotation

Answer 2

Answer: 3.0 m

Step-by-step explanation:

Moment of force about the fulcrum is equal to balance the see saw:

mg d = m'g d'

It is given that

mass of the girl, m = 30 kg

distance from the fulcrum, d = 4.0 m

mass of the boy, m' = 40 kg

Distance from the fulcrum, d' = ?

⇒30 kg×4.0 m = 40 kg× d'

⇒d' = 120 kg.m / 40 kg = 3.0 m

Thus, in order to balance the see saw, a 40 kg boy must sit at a distance of 3.0 m from the see saw.