# What is Weight: Definition and 999 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.

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7. ### Finding the weight of an object submerged in water

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8. ### How to calculate weight ratio

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### Does induced drag theory include the Lift = Weight condition?

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11. ### Why doesn't aircraft weight affect descent angle in a gliding flight

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### I Car weight is drag on uphill but thrust on downhill? (effects on fuel consumption)

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14. ### Forces on a rope when catching a free falling weight

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15. ### Work done in raising a weight

Hello The formula Mgh is commonly accepted as the work done by raising a mass by a distance h, where M is defined as the mass of the object raised. However, is this really the mass, or the weight, simply obtained by weighing the object? If it's the weight, then doesn't the equation...
16. ### Apparent weight problem (kinematics + conservation of Energy + Newton's laws)

Hello there, I have tried the problem but don't get a different of 6g's as I am supposed to. I am not sure whether I interpreted the problem in the correct way, but I would love some feedback/hints on what went wrong in my solution, thanks in advance. Solution: SITUATION DRAWINGS + FBDS so...
17. ### I Shock Load on a rope

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18. ### I Weight required to hang straight down with known torque

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19. ### I Effective weight vs distance to the point of attachment of the weight

Hi, I want to know how to calculate the effective weight if i have an object with the weight 'X' that is mounted from the side to a wall, and what happens with the weight if i increase the distance between the wall and the object. The reason i ask is as follows for the interested. I have a...
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21. ### I Calculating your weight in an elevator

I was watching one of Walter Lewin's lectures, he gave an example of a scale placed at your feet in a moving platform, apparently your weight changes when the moving platform accelerates downward, my question is if my reasoning is correct. I'm wondering why your feet stay in contact with the...
22. ### Home project: Kilogram Force on wheel bearings

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23. ### I Apparent Weight problem (falling beam)

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25. ### B What is my apparent weight in water?

Hi, I was wondering, what is my apparent weight in water? For example, when I tiptoe on land, my calf muscles are pretty much lifting all my body weight. But if I were to tiptoe with just my head out of the water, how much weight would my calves be lifting? And as I move to shallower water, how...
26. ### Pulley system to balance the weight of a person

Since we are dealing with an ideal rope, we have that ##T_1=T_2=T_3=F and T_2+T_3=2F=(m+m_p)g\Leftrightarrow F=\frac{m+m_p}{2}g.## ##T_4=3F+(m+m_p+M_p)g=\frac{3}{2}(m+m_p)g+(m+m_p+M_p)g=(\frac{5}{2}m+\frac{5}{2}m_p+M_p)g## and ##T_5=mg-2F.## Is this correct? If not, I woould appreciate a brief...
27. ### B Mass vs weight

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28. ### B Can I hold down more than my body weight on a 1 to 1 system?

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29. ### I Understanding tension and centripedal force in a puck and weight

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30. ### VTOL RC Airplane Tricopter COG, Liftoff Weight Calculations

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31. ### Engineering Calculating the percent composition of weight of an alloy

I found the density of carbon and iron: ρ_fe=7.87 g/〖cm〗^3 ρ_c=2.26 g/〖cm〗^3 Using equation 2: atom density of iron and carbon N_fe = 8.48e22 cm^-3 N_c = 1.13e23 cm^-3 Using equation 1: macroscopic scatter and absorption cross sections of iron and carbon Σ_a,fe = .217 cm^-1...
32. ### Calculate the lifting weight

how do I calculate how much force is needed to lift a horizontal metal tube to a vertical position. The metal tube is 25 feet long, weighs 300lb and and pivots 5 foot from the bottom. I will be using a hand winch and the cable attaches at the bottom of the 5 foot end of the tube.
33. ### MHB Balancing Weight on an 8m Pole: Find the Solution

A man and a boy hold opposite ends of 8m long pole which is horizontal. A mass of 200 kg is tied to the pole. If the man is to support four times as much weight as the boy where along the pole must the weight be tied? Can someone please help
34. ### Weight of gold chain when dropped on a weighing scale

The force exerted downwards on the scale by the chain when it is kept on it would be Fg= Mg =λLg where λ is the linear mass density However when the chain is dropped onto the scale it exerts an additional force due to its change in momentum The force exerted by each part of the chain would...
35. ### Tongue weight capability of 2x3x.125 steel tube at 21"?

Hello everyone. I'm building myself a half-rack for weight lifting that included 2 overhung support beams above from which to hang a safety strap incase of a failed lift. They are made from 2x3x.125 steel tube (they're Oriented with the 3" vertically). The tube are overhung by 21". How much...
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37. ### Solving the Weight Puzzle: Explaining Why and How

My solution is However can someone explain in detail why will be equal to the weight? and why does it have to be multiplied by 6?
38. ### I What does weight actually do in gyroscopic precession?

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39. ### Automotive Does vehicle weight have an effect on torque capacity of the gearbox?

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40. ### Potential Energy Storage: Investigating the Mechanics of a Heavy Weight Drop

I read about a proposal for storing potential energy by hoisting heavy weights that can be dropped when needed to generate electric power. So using the numbers from a hydraulic turbine from Hoover dam, how heavy would a hanging weight have to be to generate 178,000 horsepower as it descended...
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I’m trying to calculate the weight I have to support at one end of a pipe with flowing water. So suppose you had a water pipe that extended from the ground upwards some distance away both horizontally and vertically, i.e., at an angle. Normally, you don’t have to worry about this issue because...
42. ### What is the relationship between weight of car, power needed and speed

Hi, I'm working on a project to see if deliveries, pick ups, or both combined are better for the environment / more energy efficient / more time efficient. For example, (a) everyone collecting from a farm by bike, (b) vans bringing to supermarkets and then people collecting from supermarkets, or...
43. ### I Grip Strength: Comparing Pressure Needed to Hold 20kg Weight Plate

I am interested to compare two scenarios relating to grip strength and how much horizontal pressure will be required to hold the weight. Scenario 1: You have a 20kg weight plate in one piece. You hold the plate between your fingers. Scenario 2: You are holding a small 2X4 block of wood with a...
44. ### Speed and apparent weight of person in reverse bungee jumping

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45. ### How much weight I can spin on a motor?

Hi guys, I don't have much knowledge of physics sadly, and I want to build a machine that can spin a disk. My question is - How can I know the weight I can spin on a motor? I need to be able to spin around 5-6kg, for 350 RPM, and I'm not sure I'm aiming for the correct motor. I'm thinking of...
46. ### Calculate scaled down human model weight for practical experiment

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47. ### To find the weight of a hemisphere

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48. ### Relationship between material mass and weight

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49. ### Get the mass of an argon atom and its molecular weight from Cv

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50. ### Is my weight during the night a little bit more than during the day?

During the day, I am between sun and earth. During the night, I am behind the Earth if I'm looking from the sun. So its Day: sun-me-earth night: sun-earth-me So the forces of gravity from sun and Earth add during the night, but during the day, the sun attracts me away from the earth...