# Question regarding Moments

1. Sep 8, 2015

### Robm50

1. The problem statement, all variables and given/known data
"A child and her father are playing on a seesaw. They are exactly balanced when the girl (mass 46 kg) sits at the end of the seesaw, 2.75m from the pivot. If her father weighs 824 N, how far is he from the pivot?"

2. Relevant equations
(sum of) clockwise moment(s) = (sum of) anticlockwise moment(s)
moment (Nm) = force (N) * perpendicular distance from pivot to line of action of the force (m)

3. The attempt at a solution
girl is mass 46kg (kilograms) whilst her father has weight 824 N (newtons)?!
46 x 2.75 = y x 824
126.5 = 6.51 * 824
y = 6.51?
= 6.51 metres from pivot?

Thanks,
Robm50

2. Sep 8, 2015

### Orodruin

Staff Emeritus
6.51 * 824 is definitely larger than 126.5 - you have made an arithmetic error.

Edit: Also, the girl has mass 46 kg - not weight 46 N, which is what you seem to be assuming.

3. Sep 8, 2015

### Robm50

How would I go about solving this problem, then?

4. Sep 8, 2015

### Orodruin

Staff Emeritus
What is the weight corresponding to a mass of 46 kg?

5. Sep 8, 2015

### Robm50

That's exactly my problem; I have no idea how to find such a weight.

6. Sep 8, 2015

### Orodruin

Staff Emeritus
So, what is weight? If you do not know this you need to go back to your course literature and restudy gravitational forces.

7. Sep 8, 2015

### Robm50

Weight is the result of the gravitational attraction pulling an object's mass particles towards the Earth

Is that correct?

8. Sep 8, 2015

### Orodruin

Staff Emeritus
Weight is the force with which gravitation pulls an object towards the ground. So how do you compute this force based on the mass of an object?

9. Sep 8, 2015

### Robm50

Would it be as simple as by using the formula:

"Weight = Mass * Gravitational Field Strength"?

10. Sep 8, 2015

### Orodruin

Staff Emeritus
Yes. This will give you the weight of an object.

11. Sep 8, 2015