| Topic: |
Science > Physics |
| User: |
"Terry" |
| Date: |
04 Oct 2005 07:57:01 PM |
| Object: |
Simple physics question (from BBC website) |
This question was part of a physics 'self test' quiz (at the BBC
website)
Q:If my mass is 110kg, and acceleration due to gravity is 10 metres
per second squared, what is my weight?
a)1100Kg
b)110Kg
c)1100N
d)11N
It's a long time since I did any physics,(many, many years)
and I assumed that mass and weight (of a stationary body) would be
the same, so I gave answer 'b', which the quiz says is wrong.
Can anyone explain to me what acceleration has to do with it?
Regards,
Terry
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| User: "Clutch-3" |
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| Title: Re: Simple physics question (from BBC website) |
04 Oct 2005 10:23:28 PM |
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Hi Terry,
Actually, weight is considered a force, and as such is measured in
newtons, not kilograms. Weight is defined in terms of the
gravitational acceleration (to convince yourself of this, imagine what
your scale would say if the Earth's gravity disappeared...your mass
would not have changed, but your weight certainly would have). The
weight of a body is its mass multiplied by the acceleration of gravity,
so answer C is what you are looking for.
cheers,
Ben
Terry wrote:
This question was part of a physics 'self test' quiz (at the BBC
website)
Q:If my mass is 110kg, and acceleration due to gravity is 10 metres
per second squared, what is my weight?
a)1100Kg
b)110Kg
c)1100N
d)11N
It's a long time since I did any physics,(many, many years)
and I assumed that mass and weight (of a stationary body) would be
the same, so I gave answer 'b', which the quiz says is wrong.
Can anyone explain to me what acceleration has to do with it?
Regards,
Terry
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| User: "The Ghost In The Machine" |
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| Title: Re: Simple physics question (from BBC website) |
05 Oct 2005 12:00:06 AM |
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In sci.physics, Terry
<guitar_man@operamail.com>
wrote
on 05 Oct 2005 00:57:01 GMT
<Xns96E61E49E7BA2guitaroperamailco@193.252.117.183>:
This question was part of a physics 'self test' quiz (at the BBC
website)
Q:If my mass is 110kg, and acceleration due to gravity is 10 metres
per second squared, what is my weight?
a)1100Kg
b)110Kg
c)1100N
d)11N
It's a long time since I did any physics,(many, many years)
and I assumed that mass and weight (of a stationary body) would be
the same, so I gave answer 'b', which the quiz says is wrong.
Can anyone explain to me what acceleration has to do with it?
Regards,
Terry
It might behoove you to think of what the units of weight actually
are, and then try to combine the given quantities. However,
it's probably simpler to contemplate that mass is in kg and is
invariant regardless of gravitational pull (in one's own reference
frame), whereas weight is the force of that mass in a gravitational
field, and is proportional to both the mass and to the strength of
the field.
In short, w = mg. The correct answer is c).
The good news is that in SI it's hard to confuse the issue,
unlike Imperial pounds, where the unit of mass is actually
a slug, or the unit of force is called a poundal, depending
on which Imperial variant one wishes to try to pursue.
(It's no accident that, numerically, pounds mass =
pounds-force weight. However, the units are different.)
--
#191,
It's still legal to go .sigless.
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| User: "Steven Gray" |
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| Title: Re: Simple physics question (from BBC website) |
04 Oct 2005 10:24:51 PM |
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Terry <guitar_man@operamail.com> wrote in
news:Xns96E61E49E7BA2guitaroperamailco@193.252.117.183:
This question was part of a physics 'self test' quiz (at the BBC
website)
Q:If my mass is 110kg, and acceleration due to gravity is 10 metres
per second squared, what is my weight?
a)1100Kg
b)110Kg
c)1100N
d)11N
It's a long time since I did any physics,(many, many years)
and I assumed that mass and weight (of a stationary body) would be
the same, so I gave answer 'b', which the quiz says is wrong.
Can anyone explain to me what acceleration has to do with it?
You've been bitten by an ambiguity in the English language- and you can
expect an argument about it here. The kilogram is a unit of mass and the
newton is a unit of force. Some people contend that the term "weight"
means mass and some say that it refers to force. The writers of the test
clearly take the latter view, and the downward gravitational force on an
object is its mass times the acceleration of gravity. In their view, c
would be the correct answer.
--
Steve Gray
sgray2@cfl.rr.com
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| User: "Steve" |
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| Title: Re: Simple physics question (from BBC website) |
05 Oct 2005 05:36:32 AM |
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"Steven Gray" <sgray2@NOcfl.rr.comSPAM> wrote in message
news:Xns96E5EE522C8E9sgray2cflrrcom@65.32.5.121...
Terry <guitar_man@operamail.com> wrote in
news:Xns96E61E49E7BA2guitaroperamailco@193.252.117.183:
This question was part of a physics 'self test' quiz (at the BBC
website)
Q:If my mass is 110kg, and acceleration due to gravity is 10 metres
per second squared, what is my weight?
a)1100Kg
b)110Kg
c)1100N
d)11N
It's a long time since I did any physics,(many, many years)
and I assumed that mass and weight (of a stationary body) would be
the same, so I gave answer 'b', which the quiz says is wrong.
Can anyone explain to me what acceleration has to do with it?
You've been bitten by an ambiguity in the English language- and you can
expect an argument about it here. The kilogram is a unit of mass and the
newton is a unit of force. Some people contend that the term "weight"
means mass and some say that it refers to force. The writers of the test
clearly take the latter view, and the downward gravitational force on an
object is its mass times the acceleration of gravity. In their view, c
would be the correct answer.
Bear in mind that the same quiz had Saturn as the 4th planet from the Sun.
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| User: "PD" |
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| Title: Re: Simple physics question (from BBC website) |
05 Oct 2005 06:22:58 AM |
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Terry wrote:
This question was part of a physics 'self test' quiz (at the BBC
website)
Q:If my mass is 110kg, and acceleration due to gravity is 10 metres
per second squared, what is my weight?
a)1100Kg
b)110Kg
c)1100N
d)11N
It's a long time since I did any physics,(many, many years)
and I assumed that mass and weight (of a stationary body) would be
the same, so I gave answer 'b', which the quiz says is wrong.
Can anyone explain to me what acceleration has to do with it?
Regards,
Terry
Sure.
Weight is the force of gravity that the Earth exerts on your mass. It
is always downward, and it is just big enough that, if acting alone, it
would accelerate that mass at 10 m/s^2. If you were sitting on someone,
they would feel your weight.
If you plowed into someone while running sideways, on the other hand,
gravity (downward) is not relevant in that collision, but your mass is.
The person that you ran into would have to provide a big enough force
to slow down your mass. The more your mass, the larger that force would
have to be, which could be large enough to hurt.
PD
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| User: "Terry" |
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| Title: Re: Simple physics question (from BBC website) |
05 Oct 2005 10:52:47 AM |
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"PD" <TheDraperFamily@gmail.com> wrote in
news:1128511378.478796.129060@o13g2000cwo.googlegroups.com:
Terry wrote:
This question was part of a physics 'self test' quiz (at the
BBC website)
Q:If my mass is 110kg, and acceleration due to gravity is 10
metres per second squared, what is my weight?
Thanks for all answers.
Regards,
Terry
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| User: "Sam Wormley" |
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| Title: Re: Simple physics question (from BBC website) |
04 Oct 2005 10:33:19 PM |
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Terry wrote:
This question was part of a physics 'self test' quiz (at the BBC
website)
Q:If my mass is 110kg, and acceleration due to gravity is 10 metres
per second squared, what is my weight?
a)1100Kg
b)110Kg
c)1100N
d)11N
It's a long time since I did any physics,(many, many years)
and I assumed that mass and weight (of a stationary body) would be
the same, so I gave answer 'b', which the quiz says is wrong.
Can anyone explain to me what acceleration has to do with it?
Regards,
Terry
Weight
http://scienceworld.wolfram.com/physics/Weight.html
w = mg = 110 kg * 10 m/s^2 = 1100 kg-m/s^2
So that eliminates a) and b) as possible answers based on units.
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| User: "" |
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| Title: Re: Simple physics question (from BBC website) |
05 Oct 2005 06:35:30 AM |
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Hey, that looks like a great idea! Eliminate all human discussion!
Just refer people to the infallible Wolfram! Great!
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