Prep.2 | Newton's laws of motion | Unit 2 - Lesson 1 - Part One | Sciencee4

Описание: شرح ساينس الصف الثاني الاعدادي لغات - الفصل الدراسي الاول
شرح ساينس تانية اعدادي - ترم اول

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in this lesson:
Scalar physical quantities
Quantities that are fully defined only by magnitude.

Example
Mass. - Time.

Vector physical quantities
Quantities that are fully defined by both magnitude and direction.

Example
Force. - Acceleration.

Mass is a scalar physical quantity, while force is a vector physical quantity.
Because mass is fully defined by its magnitude only, while force is fully defined by both its magnitude and direction.

The force is measured by a device called newton meter (spring balance)

Relationship between force and motion dates back to ancient times, and among these attempts are:

The scientist Isaac Newton
• An English scientist, considered one of the most influential scientists in physics and mathematics over ages, and one of the icons of the scientific revolution.
• He formulated Newton's Laws of Motion and the universal law of gravitation, which dominated scientists' view of the material universe for three centuries until they were refined by the theory of relativity.
• He made important contributions in the field of optics.
• He developed a theory of colours based on his observations when he used a prism to analyze the white light into the colours of the visible spectrum.
• He formulated an empirical law of cooling.
• He studied the speed of sound in air.

Before studying Newton's Laws of Motion, it is necessary to understand some concepts related to force, which are:

Net force
The total force in magnitude and direction resulting from the effect of a number of forces acting on an object.

Newtons Laws of Motion
• Newton's Laws of Motion are the foundation for studying Kinematics and are expressed in simple mathematical formulas, which are useful in studying the causes of motion.
• Newton established three laws to explain and interpret the motion of objects when acted upon (affected) by one force or a number of forces, these laws are:

Newton's First Law (Law of Inertia)
The object keeps its state of rest or motion at a constant velocity in a straight line, unless acted upon by external unbalanced forces that change its state.

Newton's second law
Newton's second law explains the effect of the net force on changing the velocity of the object over time, as shown below:

Acceleration (a)
The change in the velocity of the object per unit time.
Or
The rate of change of the velocity.

Newton's second law
If a net force (F) acts on an object of mass (m), it causes the object have an acceleration (a) in the same direction as the net force.

Safety precautions
When a car stops suddenly for any reason, the driver collides with the steering wheel or the windshield, according to Newton's first law (law of inertia), so to protect the driver from rushing forward, it is necessary to consider some safety precautions such as:

Newton's Third Law
For every action, there is an equal and opposite reaction.

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