بوابة الثانوية العامة المصرية

Science primary 6th

First term

Unit One :- force and motion

LESSON ONE :- Mass and weight .

First :-Mass

MASS :-{ The amount of matter in an object .}

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G.R. The mass of the two eggs equal the mass of one searchlight.

a- (Because both the eggs and the searchlight contain the same amount of matter.

The properties of mass :-

1- The mass of an object increases when the amount of matter in it increases and vice versa.

2- All matter have mass whatever their physical states (solids , liquids , or gases.)

3- All matter have mass whatever their shapes (one piece , particles , powder , pure or mixture ).

4- All matter have mass whatever their places (in hand , on the moon or any other planet .)

5- The mass of any matter is a fixed (stable ) value and it does not change by changing :-

a- The state of matter. 2- The place of matter.

EXAMPLE:- By measuring the mass of an object on the Earth's surface, then measure the mass of the same object on the moon' surface, we will notice that its mass is not changed.

The measuring units of mass:-

Mass is measured by { gram , Kilogram or ton }

Ton

Kilogram (Kg)

Gram(g )

-It is used to measure the very big masses.

-It equals the mass of one liter of distilled water at the normal temperature.

-It is suitable for measuring large masses as fruits and vegetables

-It may equal the mass of one paper clip

-It is suitable for measuring small masses such as jewellery

*- The measuring devices of mass:-

-Mass is measured by different types of (scales ) as:-

Types of scales are

2- One-arm scale(divided into):

1- Two-arms scale (divided into)

a- One-arm digital scale

a- Balance scale: that is used to measure the large masses as cheese and vegetables.

b- One-arm scale with pointer

b- Sensitive two-arms scale:-that is used to measure small masses as gold and chemicals.

*- The mass of any solid object equals the total mass of the standard masses:-

Mass = Total mass of the standard masses.

On adding the mass of the standard masses ,we must sure that they are similar in the unit .

- The mass of the liquid = The mass of the glass with liquid – the mass of the empty glass.

Mass of liquid = M2 - M1

*-Note:- There is a relation between mass and motion.

Where , By increasing the subject's mass , it is more difficult to change its speed.

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Second :-Weight

-The reason of object's falling downward the Earth . is a type of force called (weight –( gravitational force ).

-You can feel this force when you carry an object or try lifting it.

Weight :-{ It is the force with which a body is attracted to the Earth.}

OR:-

{It is the gravitational force by which a body is attracted to the Earth}.

Scientifical vision by:-

Mr.Samir Ibrahim

Supervisor of science

-The effect of weight is always directed towards the center of the Earth .

- On Earth , all objects have weight , but in space all objects are in a state of weightlessness.

*-Newton :- {It is the measuring unit of weight and it is almost equal to the weight of an object on the Earth's surface whose mass is 100 grams.}

Question :- What is meant by the mass of a small apple is 200 grams?

a- This means that the weight (gravitational force ) of this apple equals 2 Newton.

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*- The measuring device of weight :-

-The weight of any object can be measured by the spring scale.

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*- The weight of any object can be measured by the spring scale by determining the extension of its spring.

The factors affecting weight:-

The weight of any object is affected by three factors which are :-

1)-The object's mass.

2)- The planet (place) where the object exists.

3)- The distance between the object and the center of the planet.

(1)- The object's mass :-

The weight of any object on the Earth's surface increasing by increasing the object' mass.

Weight (Newton) = Mass (kg) x 10

Note: The acceleration of the Earth gravity equals 10 m/sec2 .

(2)- The planet where the object exists:-

*- The weight of the object on the moon's surface equals one sixths (1/6) of its weight on the Earth's surface ,…(Because Earth has greater mass and gravitational force than moon.)

-As the mass of the planet (place)increases ,its gravitational force for an object increases , so the weight of the object increases.

(3)- The distance between the object and the center of the plant:-

{ The weight of any body decreases when the distance between the body and the center of the planet increases as the gravitational force decreases.}

*- The weight of a person in a balloon is smaller than that on the Earth's surface as the gravitational force decreases .

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*- Comparative Table :-

Weight

Mass

Points of comparison

-The gravitational force by which the body is attracted to the Earth.

The amount of matter in an object.

1-Defination

Newton.

Kilogram or gram or ton.

2- Measuring unit

Spring scale.

-Balance scale.

-Sensitive two-arm scale.

One-arm digital scale.

One-arm scale with a pointer.

3- Measuring device

Its effect is always directed towards the center of the Earth (downward).

It has no effect

4- The direction of its effect

Variable.

(It changes with changing the place).

Constant.

(It does not change with changing the place )

5- The changing the place

Questions on The lesson :-

(A)- Complete the following statements:-

1- Mass is a constant value and it is not affected by changing……………………………..

2- Mass is the amount of matter that body contains and it does not change according to………………………………

3- The attraction force of the Earth to the body is called …………….

GOOD LUCK Mr. samir Ibrahim