Introduction to Physics

Pressure

Pressure in Fluids – Physics 10

A fluid is a substance that offers no permanent resistance to deforming force. Fluids include liquids and gases.
Pressure is defined as force or thrust acting per unit area, the force being at right angles to the area i.e. Pressure=Force/Area. The SI unit for pressure is pascal (Pa) which equals one newton per square metre.
A pressure exerted on us and over the surface of the earth by air molecules in the atmosphere is known as the atmospheric pressure. The atmospheric pressure decreases with the increase in altitude and its unit is the atmosphere (atm) equivalent to 760mmHg or 101325Pa.
Pascal’s principle: “Pressure exerted on a contained fluid is transmitted undiminished throughout the fluid, acting in all directions and perpendicular to the walls of the container”. This has applications in hydraulic machines and jacks, syringe, drinking straws, etc.
Gauge pressure is the pressure relative to atmospheric pressure.
Absolute pressure is the sum of gauge pressure and atmospheric pressure.
Open-tube manometers have U-shaped tubes and one end is always open. It is used to measure pressure.
A mercury barometer is a device that measures atmospheric pressure.
Archimedes’ principle: “When a body is wholly or partly submerged in a fluid the upthrust equals the weight of fluid displaced (i.e. pushed aside)”. This principle is applied in ships designing, hot air balloon, submarine, etc.
Principle of floatation: “A floating body displaces its own weight of fluid.” A material floats in a fluid if its density is the same as or less than that of the fluid.
The pressure of fluids increases with depth, i.e. P=hgρ

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Introduction to Physics

INTRODUCTION TO PHYSICS – GRADE TEN PHYSICS

Physics is defined as a natural science that involves the study of nature and its motion through space-time, along with related concepts such as energy and force.
Physics principles are applied in our everyday activities such as cooking, driving, etc.
The main activity of a physicist is based on experiment in order to understand the theoretical explanations and it is mainly conducted in the laboratory.
The main causes of accidents in the laboratory are carelessness and ignorance and the most common sources of errors are Systematic, human and random errors.
When conducting an experiment remember to put on protective clothing such as overcoat, apron and gloves; and protect your eyes using goggles.
The results of experiments can be recorded using a table and used to plot a graph. From graph you can calculate the slope or gradient using the formula: Gradient G=y_(2-y_1 )/x_(2-x_1 ) =Y/X
Interpolation: is the process of using the graph to predict the reading of measurements that lie between those actually made.
Extrapolation: is the extension of the graph to include the range of the data required (common when obtaining zero on Kelvin scale)
The right-angled triangle is used to define the trigonometric functions which are common mathematical tools used in physics: sinθ=(opposite leg)/hypotenuse cosθ=(Adjascent leg)/hypotenuse tanθ=(Opposite leg)/(Adjascent leg)
Area is the extent or measurement of a flat surface bounded by length and breadth and its SI unit is the square metre.

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