What is Weight: Definition and 1000 Discussions

In science and engineering, the weight of an object is the force acting on the object due to gravity.Some standard textbooks define weight as a vector quantity, the gravitational force acting on the object. Others define weight as a scalar quantity, the magnitude of the gravitational force. Yet others define it as the magnitude of the reaction force exerted on a body by mechanisms that counteract the effects of gravity: the weight is the quantity that is measured by, for example, a spring scale. Thus, in a state of free fall, the weight would be zero. In this sense of weight, terrestrial objects can be weightless: ignoring air resistance, the famous apple falling from the tree, on its way to meet the ground near Isaac Newton, would be weightless.
The unit of measurement for weight is that of force, which in the International System of Units (SI) is the newton. For example, an object with a mass of one kilogram has a weight of about 9.8 newtons on the surface of the Earth, and about one-sixth as much on the Moon. Although weight and mass are scientifically distinct quantities, the terms are often confused with each other in everyday use (i.e. comparing and converting force weight in pounds to mass in kilograms and vice versa).Further complications in elucidating the various concepts of weight have to do with the theory of relativity according to which gravity is modeled as a consequence of the curvature of spacetime. In the teaching community, a considerable debate has existed for over half a century on how to define weight for their students. The current situation is that a multiple set of concepts co-exist and find use in their various contexts.

View More On Wikipedia.org
  1. K

    When unsuccessfully trying to lift a weight, where does my energy go to?

    Let's say I am strong enough to lift a 100 kg dumbbell, but not strong enough for a 200 kg one. If I lift the 100 kg dumbbell, I suppose the chemical energy of my body tranforms into the potential energy of the lifted dumbbell. Suppose I'm trying to lift the 200 kg one. I'm pulling as hard as I...
  2. brotherbobby

    Pulling with and without a pulley

    Let me draw a free body diagram for the man. I assume that for both cases (a) and (b), the man pulls the block up with uniform velocity. (1) In case (a), realising that the man is in equlibrium (##\Sigma F = 0##) the normal reaction on the man ##N_a = w_M + T## is given by ##N_a = (50+25)\times...
  3. T

    B How to create a parabolic formula - For Weight Loss

    Hello all I was hoping someone can help with the following problem. I am trying to create a parabolic formula to give me target weight. For example:- Day 1 = Target Weight 100kg Day 112 = Target Weight 67kg Each day is consecutive - can anyone help me to create a parabolic formula that goes...
  4. MustafaTekinay

    How much force does a moving car exert on to the road?

    I understand that the weight of the car does not change (assuming mass of the car stays the same) because of f=mg. But I am not so sure about of the aerodynamics of the car plays a role. Say, a faster car might have more air under their wheels and might exert less force on to the ground. Maybe a...
  5. T

    How to calculate jump height from the force and a person's weight

    If you want to see the video just search dwight howard sport science
  6. H

    I The irreducible representations of of su(2): Highest weight method

    Hi all I need to understand the following passage from Hall link page 78 : Some notation first: Basis for ##sl(2;C)##: ##H=\begin{pmatrix} 1&0\\0&−1\end{pmatrix} ;X=\begin{pmatrix} 0&1\\0&0\end{pmatrix} ;Y=\begin{pmatrix} 0&0\\1&0\end{pmatrix} ## which have the commutation relations...
  7. J

    Hanging weight generates PSI?

    Hello; I have a quick question that has me thinking. Please note that i don't much like working with imperial units because there is one too many polysemous words. Say i had a 1 lb weight hanging on a 1in diameter rope. (rope weight neglected) 1. Could you say that at any perpendicular cross...
  8. C

    Ideal Ball weight to get the maximum range from a ball launcher?

    Hello guys, i am building a ball launcher to proper a line of baits into the sea, the line has 25 baits, each bait weights 30 grams (about 1oz) ideal shooting degree seems to be 45 to get maximum range, What I would like to figure out is the ideal weight of the ball to achieve the greatest...
  9. brotherbobby

    Apparent weight of body immersed in liquid

    I have to assume that ##h## is the height of the body. The graph above shows how the apparent weight of the body changes as it is immersed into the liquid. In (a), after immersing the whole height of the body, the apparent weight ##W_{\text{app}} > 0##. Hence the upthrust ##U < w_B \Rightarrow...
  10. brotherbobby

    Weight of water with objects floating

    We understand that the crucial thing about the problem is that the volume of water present in the three containers are not the same. Also, we note that in each case the weight of the container is the total weight of its contents. (A student might be confused as to why should be so - after all...
  11. S

    Spring pendulum with and without weight

    Equations provided: for a spring pendulum and m replaced with L and k with g for the same pendulum, but with no weight attached. Greetings I tried solving this by stating that the length is 0,50m (since no length of the spring is given) and turning around the equation for the spring...
  12. PeterDonis

    I Does the statistical weight of data depend on the generating process?

    The specific example I'm going to give is from a discussion I am having elsewhere, but the question itself, as given in the thread title and summary, is a general one. We have two couples, each of which has seven children that, in order, are six boys and one girl (i.e., the girl is the youngest...
  13. C

    F=ma experiment: Trolley being pulled by a falling weight

    The weight accelerating/pulling the trolley is changed and corresponding acceleration recorded. What I don’t understand is why the weight added/removed to the hanging weight is removed/added to the trolley
  14. archaic

    Chemistry How to Calculate the Percent Weight of Components in a Gas Mixture?

    The total molar mass is ##M=\frac{dRT}{P}=\frac{1.98*0.08206*(63+273.15)}{750/760}=55.3454786\,g/mol##. We have ##M=aM_1+bM_2## where ##M_1## and ##M_2## are the molar masses of ##\mathrm{NO_2}## and ##\mathrm{N_2O_4}## respectively. If I consider ##n## moles, I'd have...
  15. N

    Bouyancy Question: Two weights on strings, with one weight submerged

    Hi new to the physics world and the symbiology is hard to understand completely. Attached is the work I've done to a final solution but I can't seem to get the answer in terms of only density of water and T1 and T2. Thank you for any assistance. [ Mentor Note -- Word file replaced with a...
  16. M

    Weight distribution of 2 configurations

    Say Object-A weighs 100 lbs. In Figure-1, it's obvious that the weight distribution is even along the bottom edge of Rectangle-B. In Figure-2, ignoring the weight of the white objects, is the weight distribution exactly the same along the bottom edge of Rectangle-B as it is in Figure-1?
  17. CheesyPeeps

    Force on side of tank filled with liquid of variable specific weight

    Homework Statement: An open tank with a rectangular side 1 m wide and 4 m high is filled with a liquid of variable specific weight, γ, with γ = 50 + 2y (N/m3), where y is measured vertically downward from the free surface. Find the magnitude of the force on the side of the tank. Homework...
  18. T

    Engineering Help With Mass and Weight Units

    Hello all I was hoping someone could clear up the units & difference between Mass and Weight. I live in the UK. I weighed myself today on the scale and the scale told me that I weighed 95kg. What bothers me is that if:- Mass - Is the amount of "stuff" I am made from which is measured in kg...
  19. W

    Rule of Thumb for the weight of a filling meal?

    Hi, Just doing some informal research: what is the average weight of a full meal ( meaning it allows you to feel full after eating it) for a man /woman? Internet doesn't say much ; only found two posts both suggesting around 1lb . Anyone else know? Edit: My goal is to decide whether the price...
  20. T

    Conservation of Energy of a Spring with Weight Added

    I'm all messed up on this problem. I see you can get the solution (74cm, as listed in the back of the book) by simply setting mgh=1/2kx^2, saying that h=x, and then adding 15 cm to that since that's the original length of the spring. This is the solved solution I was given. But now I think...
  21. D

    MCNP: mesh with weight window generator

    Hallo everybody, I am using a mesh-based-weight window generator. It is clear to me that the coarse mesh must cover the full geometry; my doubt is about the fine mesh. Is it possible to define the fine mesh only in a part of a geometry, for example telling to MCNP to make 5 bins between y1 and...
  22. CherryB

    Is weight a better way to derive energy than flow?

    I am trying to figure out the total energy a system of falling buckets can produce, and whether it would be a system that can replace or enhance a system of turbines in a hydroelectric dam situation. I need to figure out the total energy that a system of buckets, suspended on a chain system...
  23. karush

    MHB 5.1.313 AP Calculus Exam DE on bird weight

    I just posted a image due to overleaf newcommands and graph ok (a) if we use f(20) then the $B=0$ so their no weight gain. (b), (c), was a little baffled and not sure how this graph was derived...
  24. T

    I Does the superposition have a weight?

    Consider the double slit experiment performed on a extremely sensitive scale, whereby the whole device including source and detector is isolated. From energy conservation we would expect that the weight is constant in principle while the experiment is running. What would we conclude? That the...
  25. T

    What Does Unit Weight (kN/m^3) Mean?

    Hello This is a really silly question but I have doubted myself and I was wondering if anyone could help. I have been given the following information:-I am trying to understand what it means when the title states Unit Weights? I thought these were density but density is kg/m^3 - whereas these...
  26. M

    I How to handle the infinity when making a least square fit for the first point?

    Hello! I have 5 data points with errors associated to them ##y_i \pm dy_i## and the corresponding ##x_i## values (which don't have uncertainties associated to them). I need to calculate the difference between the first of these points, ##y_1## and the rest, and fit a straight line to it...
  27. Addez123

    What is the correct way to solve for weight on two pulleys?

    I've done this exercise twice now, the answer is 1.4m/s but I get 1.64m/s. It's too far off to be rounding error. 1. I don't use energy consideration, because I don't have a clue how that would work. 2. I still need to know what's wrong with my current way of solving this. Any help is...
  28. W

    Can I readily clamp a pipe with 450 weight without it slipping?

    I'm planning on lifting a submersed well pump that is hanging on a 80' 2" galvanized pipe. Total weight is estimated to be 447lbs based on: pump ~ 50lbs pipe 3.6lbs per foot water 1.36lbs per foot The plan is to use two pieces of wood (1 foot of 2x6) with two clamps to hold the pipe in place...
  29. BFC

    How to Calculate Weight on Pedals from Watts?

    Summary: How to calculate weight on pedals? For example, a bicycle pedal manufacturer might say that their pedals have a max rider weight of 120kg (264lbs). First off, since the rider is sitting on the saddle, I'm not sure how this would really impact max pedal weight? Going forward, these are...
  30. S

    Solving for weight and mass in kg in an elevator

    Fn= normal force W=mg W=(65)(9.8)= 637N Fn-637= -(65)(0.2*9.8) Fn= 509.6N I got the weight of the woman in the elevator, but I have trouble finding what the scale reads in kg. I was given the solution which read: a = (g-0.2g)= 0.8g W= 0.8g*509.6N= 52kg. My questions 1. why do I have to...
  31. I

    Weight Distribution Across Multiple Points

    Thanks in advance to anyone that can help me solve this problem, its causing me a real headache. I need to transport a rather large frame that supports a large heavy item. The weight is not evenly distributed along its length. I know the various distances between the supports, the total weight...
  32. E

    Force equation: use mass or weight?

    I require to calculate acceleration of an object caused by a force of 100N acting upon it. The weight of the object is 0.5kg I'm using the equation F = m * a Is it correct to use weight of the object instead of mass in the equation. Will it yield correct results? Or would I need to calculate...
  33. Kaushik

    Why does the apparent weight decrease when a body accelerates down a rope?

    When a body accelerates down(climbs down) a rope, why does its apparent weight reduce? Oh wait, does it even reduce in the first case? If yes, is it because of the Newtons first law of motion, which states that a body in motion tends to be in motion and a body at rest tends to be at rest. So...
  34. nuuskur

    Effects of velocity on weight (mass?)

    A ballistics-esque question. Suppose we are driving at ##x \text{ m/s}## and we have to suddenly brake. For students in driving schools they are told something along the lines of "during the braking, the body experiences ##y \text{ kg}## of force" or "the mass of the body is much higher than at...
  35. G

    Automotive How much power is needed to haul a weight up an incline at a certain speed

    Good afternoon everyone, I need help with a certain calculation. How much power is needed to pull a 250lb load up a 45 degree incline at 5 mph. I am working on a project at school and would like to know what kind of motor we can use. Thank you very much!
  36. Lars278

    Why is there no r^2 term in the formula for the swing weight of a golfclub?

    The Swing Weight of a golfclub = m * (r - 14) m = mass of the club in grams r = distance from the top of the shaft to the center of mass of the club in inches 6050 equals the swing weight D-0 But the formula for the angular acceleration of any object spinning around an axis is: ωdot = τ / I In...
  37. brotherbobby

    The Indeterminacy of Problems with Multiple Friction Interfaces

    For convenience, I have marked the C.G. of the sphere as ##G_S## and that of the bar only as ##G_B##. The C.G. of the combination is halfway between them, shown by the green ##G_C##. My answer is that the combination will rotate about ##G_C## (centre of the bar) as it falls. I wonder if I am...
  38. S

    How Bicycle Wheel Rim weight changes forward acceleration?

    How much faster will a bicycle accelerate forward if both front and rear wheel rims are changed for lighter ones? Power input, size, hubs, spokes tyres, Frame etc all staying the same. I can give you any sizes and weights needed, let me know what is needed for this calculation and I’ll reply...
  39. M

    Mechanics of Solids - weight problem

    Summary: How much weight can the bars support? Three one-meter-long bars with cross-section area A = 1 square centimeter support a rigid plate of weight W. For steel, E = 200 GPa and S = 400 MPa. Determine the maximum weight W the bars can support for three cases: (i) all three bars are...
  40. T

    What is the mean moleculer weight of the gas at the solar core?

    Here, i have provided the description of the mean molecular weight from my course notes as well as my workings. I'm not sure about my values for X and Y. It states that X=1 if all of the hydrogen is ionised which i think the 1 represents 100% hydrogen but the core is also made up...
  41. koiuuuuuuuuuuu

    Weight vs. Mass: Explaining the Difference

    In class we do Science and I have faced with the problem between Weight and mass. Tutor told us that the weight is the force that causes everything to move. Mass is the kg .Why then, people ask other people what weight are you? Explain please. Thanks
  42. Anie Nancu

    How is an object's weight distributed among the fours legs of a table?

    When I place an object in a table, how is the weight distributed in the four legs? Is there an mathematical calculations for that?
  43. R

    How did 19th century scientists measure atomic and molecular weight?

    Found myself wondering about this recently, though I can't recall the context. When Mendeleev proposed the periodic table of elements, I believe that it was known that atomic weights of the known elements were multiples of hydrogen's atomic weight. Presumably also with substances like oxygen...
  44. P

    A Highest weight of representations of Lie Algebras

    Hello there, Given a Lie Algebra ##\mathfrak{g}##, its Cartan Matrix ##A## and a finite representation ##R##, is there a way of determining its highest weight ##\Lambda## in a simple way? In my course, we consider ##\mathfrak{g}=A_2= \mathfrak{L}_{\mathbb{C}}(SU(3))##. It is stated that the...
  45. T

    Slab resting on two supports: Maximum weight added without tipping?

    Hi, My attempted solution is in the image: I choose the edge on the left side, but the solution should be similar on both sides (just substitute C for A). (I missed to multiply by "g" in F_2.) Is this the correct way of thinking? I'm not sure about the distance "D".
  46. N

    What are the dimensions of angular acceleration divided by radius?

    Hey guys, so I am a little stumped on this problem. Can y'all help? I think for a) it is true but am not sure For b) I believe is is false because the angular acceleration would cause the angular speed to increase For c) I think it is true since acceleration is constant so T=ma is constant Does...
  47. LordGfcd

    Compression of an object under it's own weight.

    Let's first consider a cube side length a, mass m, Young's modulus of the block is E. How do we calculate the decrease of the height of the center of mass of that cube ?
  48. G

    What is the radiation weight factor?

    Homework Statement A dose of 5 Gy of X-rays is required to destroy 63% of a particular bacterial population. It requires 1 Gy of beta particles of mean energy 1.0 MeV to accomplish the same result. What is the wR for the beta particles in this population of bacteria? Homework Equations H= (wR)...
  49. K

    What is the weight that will balance the object Q?

    Here is diagram for Tower Crane. The Rack weight P=700kN, and the maximum load capacity for this crane is W=200kN. The long beam length is 12 metres, and the balance object weighs Q. The short beam length is 6 metres. What is the weight of Q to keep the crane's balance at all situation?
  50. S

    Is it possible to "redistribute" the weight of the table....?

    I am a total physics novice, so please bear with me. I would like to know if it would even be possible to achieve this result. Assume I have a fixed abject like a table. Would it be possible to "redistribute" the weight of the table such that the front end of the table bears more of the...
Back
Top