Physics Help Forum Basic Question - Mass vs Weight

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 Oct 3rd 2018, 07:26 AM #1 Junior Member   Join Date: Oct 2018 Posts: 3 Basic Question - Mass vs Weight My daughter had a question from school and it confused me. The question reads: True of False; Both weight and mass measure how heavy (or light) an object or a substance is. My daughter circled false and I agree with her. But she missed that question. Mass is different than weight. Weight changes depending on where you are and mass stays constant. Can anyone help? Thank you! Last edited by GingerNinja; Oct 3rd 2018 at 08:33 AM.
 Oct 3rd 2018, 11:00 AM #2 Senior Member   Join Date: Aug 2010 Posts: 434 I really don't like the way this question is worded! Exactly what is intended by "measure how heavy"?
 Oct 3rd 2018, 11:11 AM #3 Junior Member   Join Date: Oct 2018 Posts: 3 She's in 5th grade btw.
 Oct 3rd 2018, 05:10 PM #4 Senior Member   Join Date: Apr 2017 Posts: 498 Yes ... the question is designed to confuse , as many are. The unseen people who created the education system have the aim of dumbing people down , preventing learning ...Search " The Deliberate Dumbing Down of America": A Chronological Paper Trail Book by Charlotte Thomson Iserbyt But lets look at the question "True of False; Both weight and mass measure how heavy (or light) an object or a substance is..." "Heavy" is a measure of force .... units are Newtons Is weight a measure of force ???? .....YES Is mass a measure of force ???? ....Most definitely NOT! units are Kg So beyond all doubt the correct answer is FALSE Last edited by oz93666; Oct 3rd 2018 at 05:22 PM.
 Oct 4th 2018, 09:36 AM #5 Junior Member   Join Date: Oct 2018 Posts: 3 Thank you oz93666! I will keep an eye on her schooling so she doesn't become one of the "dumbing down." HAHA I have yet to hear from the teacher, but I will update this post with her response. oz93666 likes this.
 Oct 4th 2018, 09:54 AM #6 Senior Member   Join Date: Oct 2017 Location: Glasgow Posts: 424 Mass is no longer a good indicator of heaviness if you consider a sample of objects at different locations and those locations have different local gravitational field strengths. Therefore, generally speaking, the answer is false. However, if you take a sample of objects at the Earth's surface where g is constant, both weight and mass measurements are an indication of the heaviness of something. The question presumably has this assumption and a better worded question would state it. At the sort of level of schooling you're talking about, chances are the context of every question is something happening on the Earth's surface using "normal" everyday conditions, so it's a reasonable assumption. Last edited by benit13; Oct 4th 2018 at 09:58 AM.
 Oct 5th 2018, 02:45 AM #7 Senior Member   Join Date: Apr 2015 Location: Somerset, England Posts: 1,035 I am not american but I see that the average age of 5th graders is 10/11. I well remember at that age in an English school being slapped down following a BBC science programme for schools, where the presenters said "An object floats because it is lighter than water and sinks because it is heavier than water." When our teacher asked the class "Why does something float" I put up my hand and said "Because it is less dense than water" and was told I was wrong. In England few teachers of that age group have any science at all to their name. Most are nice people who like looking after smaller children (and keeping them quiet). These days some are PE specialists and so on. So to your question. No the school were wrong and your daughter was right. I hope she can take this incident in her stride and it does not put her off science. When she is older they will tell her a better story.
 Oct 5th 2018, 05:15 AM #8 Senior Member     Join Date: Jun 2016 Location: England Posts: 959 Looks to me like one of those questions where by trying to simplify the sentence used, the precision needed was lost. If the sentence was: Both weight and mass indicate how heavy (or light) an object or a substance is. Then we could accept that as true. however the term "measure" has particular connotations which encompass the units in which the quantities are measured, Thus weight is (properly) measured in Newtons and Mass in Kilograms (which are different beasts) These two qualities are related by the proverbial F=ma Replace the acceleration term by the acceleration due to gravity (F=mg) and you have an expression relating Mass to Weight. Note that the assumption that "g" is constant is not entirely true. The Earth is not a perfect sphere so "g" varies with latitude, it also varies with local geology. So weight will be different when measured at the north pole or at the equator, but mass will be the same. __________________ ~\o/~
Oct 5th 2018, 05:47 AM   #9
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 Both weight and mass indicate how heavy (or light) an object or a substance is.
There's more to it than that.

What is the weight of an object floating in water compared to standing on the table?

What is the mass of that object floating in water compared to standing on the table?

 Oct 6th 2018, 10:18 PM #10 Physics Team   Join Date: Apr 2009 Location: Boston's North Shore Posts: 1,576 Woody is referring to the fact that the greater your mass is the greater your weight is and vice versa. We often determine the mass of a substance by how much it weighs. I.e. W = Mg. Therefore M = W/g. In chemistry we always determined mass using a weight scale (calibrated for earth). BTW - Woody said that mass indicates weight, not is weight.

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