Measurements

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1.general physics  1.1 length and time  -i-Physical Quantity Physical Quantities A physical quantity is a property of an object that can be measured with a measuring instrument. A physical quantity is usually expressed as “a magnitude ( numerical value)  and a  physical unit or more ” Example :- Normal body temperature of a healthy human being is  37  0 C -ii-Length Measuring Length. Length is “the distance between two points in a space”. According to SI units, the length quantity is expressed in meter. There are several kinds of measuring devices used to measure quantity of length, among others, are as follows. Tools used… a-   Measuring tape. b-   Ruler c-   Vernier callipers. d-    Micrometer Measurement of length Length is measured accurately through many meth...
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Mass weight and density

MASS AND WEIGHT AND DENSITY


Weight = force of gravity = mass x free fall acceleration = ma = mg
Force = Weight = mg
 the acceleration of free fall for a body near to the Earth is constant
Notes:-
10 m/s2 = 10 N/kg
  •  Weight is the force which causes an object to accelerate downwards and has the value mg.
  • The value of the acceleration caused by weight can be calculated from Newton’s second law, using the equation F = ma
  • Weight unit is N (because it is a force)
  • It is measured by spring balance


 Mass  Weight
DefineIt is the amount that body contains“It is not a force”It is the force of gravity acting on the body“It is a force”
UnitskgN (kg.m/s2)
Scalar or vectorScalar quantity(No direction)Vector quantity(always vertical downwards)
Device used to measurePan balance.Beambalance.Spring balance
Dependence on placeMass of a body remains the same throughout the universe
(doesn’t change from one place to another)		Weight varies from one place to another depends on the value of (g) which is the acceleration due to gravity.
The relationship between them

Weight = mg

Notes:-
  1. The weight of any object on the moon is 1/6 its weight on the earth, so gmoon = 1.67 m/s2.
  2. If the weight of 1kg mass will be 10 N, and since the weight = 10 x mass, so if you measure your weight on a scale (on earth) and your weight was 600 N, we can write it on the scale as 60 kg.
  3. The acceleration due to gravity is constant at the same place and height, can be taken as …… 10 m/s2.
  4. Free fall acceleration = g = weight / mass = constant (10 m/s2)
Credits:   https://hgphysics.com/gph/c-forces/1-force-and-motion/weight/

Density credits: znotes

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