وزن

This page is about the physical concept. In law, commerce, and in colloquial usage weight may also refer to mass. For other uses see weight (disambiguation).

الوزن هو قوة جذب الأرض للجسم. وهي طريقة لتحديد كمية مادة ما، تختلف وحدات أو معيارية الأوزان من مادة ما إلى أخرى عند قياسها فبعضها مخصص للأوزان القليلة أو الخفيفة أو الثمينة ومنها ما هو للتحديد التقريبي للمادة.

وزن
ميزان زنبركي لقياس وزن غرض.
الرموز الشائعة	$W$
الوحدة الدولية	نيوتن (N)
وحدات أخرى	pound-force (lbf)
In الوحدة الدولية الأساسية	kg⋅m⋅s−2
بعد قياسي SI	${\mathsf {MLT}}^{-2}$
Extensive?	Yes
Intensive?	No
Conserved?	No
اشتقاقات من كميات أخرى	$W=mg$ $W=ma$
البعد	${\mathsf {MLT}}^{-2}$

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التاريخ

Ancient Greek official bronze weights dating from around the 6th century BC, exhibited in the Ancient Agora Museum in Athens, housed in the Stoa of Attalus.

Weighing grain, from the Babur-namah

تعريفات

This top-fuel dragster can accelerate from zero to 160 kilometres per hour (99 mph) in 0.86 seconds. This is a horizontal acceleration of 5.3 g. Combined with the vertical g-force in the stationary case the Pythagorean theorem yields a g-force of 5.4 g. It is this g-force that causes the driver's weight if one uses the operational definition. If one uses the gravitational definition, the driver's weight is unchanged by the motion of the car.

Several definitions exist for weight, not all of which are equivalent.

التعريف الثقالي

The most common definition of weight found in introductory physics textbooks defines weight as the force exerted on a body by gravity. This is often expressed in the formula W = mg, where W is the weight, m the mass of the object, and g gravitational acceleration.

الكتلة

An object with mass m resting on a surface and the corresponding free body diagram of just the object showing the forces acting on it. Notice that the amount of force that the table is pushing upward on the object (the N vector) is equal to the downward force of the object's weight (shown here as mg, as weight is equal to the object's mass multiplied with the acceleration due to gravity): because these forces are equal, the object is in a state of equilibrium (all the forces and moments acting on it sum to zero).

المقالة الرئيسية: Mass versus weight

الأرض تجذب الاجسام بقوة تؤثر باتجاه رأسي إلى أسفل تسمى قوة الجاذبية الأرضية ، و اتفق العلماء على تسمية قوة جذب الأرض بوزن الجسم و يستخدم الميزان الزنبركي في قياس الأوزان.

This table shows the variation of acceleration due to gravity (and hence the variation of weight) at various locations on the Earth's surface.

Location	Latitude	m/s2
Equator	0°	9.7803
Sydney	33°52′ S	9.7968
Aberdeen	57°9′ N	9.8168
North Pole	90° N	9.8322

The historic use of "weight" for "mass" also persists in some scientific terminology – for example, the chemical terms "atomic weight", "molecular weight", and "formula weight", can still be found rather than the preferred "atomic mass" etc.

In a different gravitational field, for example, on the surface of the Moon, an object can have a significantly different weight than on Earth. The gravity on the surface of the Moon is only about one-sixth as strong as on the surface of the Earth. A one-kilogram mass is still a one-kilogram mass (as mass is an intrinsic property of the object) but the downward force due to gravity, and therefore its weight, is only one-sixth of what the object would have on Earth. So a man of mass 180 pounds weighs only about 30 pounds-force when visiting the Moon.

SI units

In most modern scientific work, physical quantities are measured in SI units. The SI unit of weight is the same as that of force: the newton (N) – a derived unit which can also be expressed in SI base units as kg⋅m/s² (kilograms times meters per second squared).

In commercial and everyday use, the term "weight" is usually used to mean mass, and the verb "to weigh" means "to determine the mass of" or "to have a mass of". Used in this sense, the proper SI unit is the kilogram (kg).

Pound and other non-SI units

In United States customary units, the pound can be either a unit of force or a unit of mass. Related units used in some distinct, separate subsystems of units include the poundal and the slug. The poundal is defined as the force necessary to accelerate an object of one-pound mass at 1 ft/s², and is equivalent to about 1/32.2 of a pound-force. The slug is defined as the amount of mass that accelerates at 1 ft/s² when one pound-force is exerted on it, and is equivalent to about 32.2 pounds (mass).

Sensation

انظر أيضاً: Apparent weight

The sensation of weight is caused by the force exerted by fluids in the vestibular system, a three-dimensional set of tubes in the inner ear.Sensation of Weight^{[محل شك]} It is actually the sensation of g-force, regardless of whether this is due to being stationary in the presence of gravity, or, if the person is in motion, the result of any other forces acting on the body such as in the case of acceleration or deceleration of a lift, or centrifugal forces when turning sharply.

Measuring

المقالة الرئيسية: Weighing scale

"Weigh" تحوّل إلى هنا. لمطالعة other uses، انظر Weigh (disambiguation).

A weighbridge, used for weighing trucks

Relative weights on the Earth and other celestial bodies

المقالة الرئيسية: Earth's gravity and Surface gravity

The table below shows comparative gravitational accelerations at the surface of the Sun, the Earth's moon, each of the planets in the solar system. The “surface” is taken to mean the cloud tops of the gas giants (Jupiter, Saturn, Uranus and Neptune). For the Sun, the surface is taken to mean the photosphere. The values in the table have not been de-rated for the centrifugal effect of planet rotation (and cloud-top wind speeds for the gas giants) and therefore, generally speaking, are similar to the actual gravity that would be experienced near the poles.

Body	Multiple of Earth gravity	Surface gravity m/s2
Sun	27.90	274.1
Mercury	0.3770	3.703
Venus	0.9032	8.872
Earth	1 (by definition)	9.8226
Moon	0.1655	1.625
Mars	0.3895	3.728
Jupiter	2.640	25.93
Saturn	1.139	11.19
Uranus	0.917	9.01
Neptune	1.148	11.28

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وحدة قياس الوزن

يقاس الوزن بوحدة دولية تسمى (نيوتن) نسبة إلى العالم الإنجليزي اسحق نيوتن الذي وضع القانون العام للجاذبية، و النيوتن يساوي تقريبا قوة جذب الأرض لكتلة مقدارها 100 جرام.

و فيما يلي بعض المعايير:

• الرطل = 450 جرام
• أوقية = 37.5 جرام
• مثقال = 4.680 جرام ( وزن 65 حبة شعير )
• الدرهم = 3.125 جرام ( وزن 48 شعيرة )
• الحمصة = ربع مثقال
• الجوزة = 4 مثاقيل
• الدانق = 0.525 جرام ( وزن 8 شعيرات )
• القيراط = 0.198 جرام ( وزن 4 شعيرات )
• حبة شعير = 0.049 جرام
• ملعقة الطعام الكبـيرة و هي تعادل وزن مثقال و يعادل وزن 65 حبة شعير تقريباً
• ملعقة الطعام وسـط و هي تعادل نصف مثقال ويعادل وزن 33 حبة شعير تقريبا
• ملعقة الطعام صـغيرة و هي تعادل ربع مثقال ويعادل وزن 17 حبة شعير تقريباً

أمثلة

إذا كانت كتلة الجسم (200) جرام فإن قوة جذب الأرض له تساوي 2 نيوتن. أي أن وزنها = 2 نيوتن و الجسم الذي كتلته (300) جرام فإن وزنه = 3 نيوتن. و إذا كانت كتلة الجسم (1000) جرام أي (1) كجم فإن قوة جذب الأرض له = 10 نيوتن. أي أن وزن الكيلو جرام الواحد على سطح الأرض = 10 نيوتن. و إذا قلنا أن جسما كتلته 2 كجم فإن وزنه = 2 × 10 = 20 نيوتن. و إذا قلنا أن جسما كتلته 5 كجم فإن وزنه = 5 × 10 = 50 نيوتن.

القانون

             وزن الجسم = كتلة الجسم × وزن الكيلو جرام الواحد
                 
                 و    =     ك     ×    ج
               
                 |          |          |
               نيوتن     كيلو جرام   نيوتن / كيلو جرام

انظر أيضاً

ابحث عن gross weight في
قاموس المعرفة.

• Human body weight
• weight the English unit