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Physics/difference between mass and weight


QUESTION: Hello sir can you differentiate vector and scalar quantity. for example if a car is not moving and if we say this car runs at the speed of 160km per hour is a scalar and if a car is moving in some direction it is vector.If I am wrong pls. describe me

ANSWER: That's one example.  We usually think of scalar quantities as those which have a magnitude and no inherent direction, like mass.  There's no direction associated with mass or charge.  But you're right, "speed" and "velocity" are different in that one is just a magnitude that you'd read on a gauge, and one is a vector that you could plot on a map.

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QUESTION: Is there any difference between speed and magnitude where we should use the word magnitude and where we should use the word speed in our contest. Thank you for guiding me and clearing my doubts

ANSWER: Speed is a quantity.  The size of any quantity is its magnitude.  Vectors have a "size" given by the root of the sum of the square of their components.  That is their magnitude.  Speed is a specific type of quantity with its own unit.  Magnitude is just a word that means size.

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QUESTION: what is difference between mass and weight. weight is one which depends on gravitational force the more the gravitationl for an object more the weight pls. say me about the mass both are same or it depends on the size of the weight pls. explain

No, weight is a force, like you said...but mass is a property of an object.  Weight depends on the object's mass and the gravitational pull.  Mass never changes.  Mass is the same in zero gravity.  It still takes a force to accelerate a mass.  See here:


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Dr. Stephen O. Nelson


I can answer most basic physics questions, physics questions about science fiction and everyday observations of physics, etc. I'm also usually good for science fair advice (I'm the regional science fair director). I do not answer homework problems. I will occasionally point out where a homework solution went wrong, though. I'm usually good at explaining odd observations that seem counterintuitive, energy science, nuclear physics, nuclear astrophysics, and alternative theories of physics are my specialties.


I was a physics professor at the University of Texas of the Permian Basin, research in nuclear technology and nuclear astrophysics. My travelling science show saw over 20,000 students of all ages. I taught physics, nuclear chemistry, radiation safety, vacuum technology, and answer tons of questions as I tour schools encouraging students to consider careers in science. I moved on to a non-academic job with more research just recently.

Ph. D. from Duke University in physics, research in nuclear astrophysics reactions, gamma-ray astronomy technology, and advanced nuclear reactors.

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