Do I weigh 50 kg or 50 * 9.8 kg?

In summary, On Earth, an average person's mass is around 50 kg, which translates to a weight of 490 Newtons. However, on the moon, the lower gravity would result in a weight of 81 Newtons. Most weighing scales are designed to measure weight, not mass, and are marked in kg for convenience. To confirm that your scale is measuring weight, you can push down on it and see the reading increase. On Ceres, a dwarf planet with even lower gravity, the weight would be 21 Newtons.
  • #1
Phys12
351
42
When I take my weight, it often shows around 50 kg. However, in my Astronomy class currently, it was mentioned that an average person's mass is roughly around 50 kg.

So, which one of them is correct? It doesn't make sense for my weight to be 50 kg because kg isn't exactly a unit of force, but then do I really weigh 490 N? (I'm so fat!)

Thanks!
 
Physics news on Phys.org
  • #2
On Earth your mass is 50kg and your weight (the force you exert on the ground) is 490 Newtons.

On the moon your mass would still be 50kg but your weight would be 81 Newtons because gravity is lower.

Most weighing scales (unsurprisingly) measure weight not mass but because they are intended for use on the Earth only they are marked in Kg because that's what people are familiar with. They won't work correctly on the moon.
 
  • #3
Phys12 said:
(I'm so fat!)
Just say you weigh .5 kN.
 
  • #4
http://www.learnwithmac.com/2015/03/27/what-do-scales-measure/

..how do you know that your scale is actually reading force [weight] and not mass? Well there is an easy way to confirm this. Stand on your scale close to a fixed object and then carefully push yourself down on the scale using the fixed object as a support. You will suddenly see the scale reading increasing, indicating that your mass has increased. However this is not the case since you haven’t suddenly put on mass.
 
  • #5
I only weigh 21 Newtons**(on Ceres)
 
  • Like
Likes Biker and fresh_42
  • #7
 

Related to Do I weigh 50 kg or 50 * 9.8 kg?

1. How do I convert my weight from kg to Newtons?

The unit of weight in the metric system is Newtons (N), not kilograms (kg). To convert your weight in kilograms to Newtons, you must multiply your weight by the acceleration due to gravity (9.8 m/s²).

2. Why is weight measured in Newtons instead of kilograms?

Weight is a measure of the force of gravity acting on an object, so it is measured in Newtons. Kilograms, on the other hand, are a unit of mass, not weight. The confusion may arise because we often use the term "weight" colloquially to refer to our body mass.

3. What does it mean if I weigh 50 kg or 50 * 9.8 kg?

If you weigh 50 kg, it means that your body has a mass of 50 kilograms. If you weigh 50 * 9.8 kg, it means that your body has a weight of 50 Newtons, which is equivalent to 50 kg multiplied by the acceleration due to gravity (9.8 m/s²).

4. Is it possible to weigh the same in kilograms and Newtons?

No, it is not possible to weigh the same in kilograms and Newtons. As mentioned before, kilograms measure mass, while Newtons measure weight. However, if you are asking whether it is possible to have the same mass and weight, the answer is yes. This would be the case if you were in a location where the acceleration due to gravity is 1 m/s², such as in outer space.

5. Why do we use the acceleration due to gravity in weight measurements?

The acceleration due to gravity is used in weight measurements because weight is a force that results from the gravitational attraction between an object and the Earth. The acceleration due to gravity varies depending on the location and altitude, but it is typically considered to be 9.8 m/s² for most calculations on Earth.

Similar threads

  • Other Physics Topics
Replies
19
Views
1K
  • Introductory Physics Homework Help
Replies
1
Views
2K
  • Other Physics Topics
Replies
2
Views
1K
  • Mechanical Engineering
Replies
6
Views
1K
  • Engineering and Comp Sci Homework Help
Replies
7
Views
1K
  • Other Physics Topics
2
Replies
63
Views
14K
  • Other Physics Topics
Replies
4
Views
4K
  • Other Physics Topics
Replies
3
Views
2K
Replies
1
Views
1K
Replies
8
Views
136
Back
Top