Pressure

When you stretch a rubber band or a spring, it pushes back against you because elastic materials store energy when deformed. This stored energy creates tension in the material—think of it like the string is trying to return to its original state. The pressure or stress in an elastic string depends on how much you've stretched it and the material's resistance to stretching. A practical example is a Nigerian woman using a rubber band to tie her hair; the tension in that rubber band creates pressure on her hair, and you can feel this tension if you try to stretch it further.

The relationship between how much something stretches and the force it produces is called Hooke's Law. Understanding elastic strings helps explain how cables support bridges, how springs work in vehicles, and even how bones resist breaking under pressure.

Pressure is simply the force acting on a surface divided by the area over which that force spreads. Think of it like this: when you stand on the ground, your weight pushes down on the earth below you. The SI unit for measuring this pushing effect is the Pascal, written as Pa. One Pascal equals one Newton of force spread over one square meter of area.

You encounter pressure daily in Nigeria. When you use a bicycle pump to inflate a tyre, you're creating pressure by concentrating force into a small area. The tighter the pump's opening, the more pressure builds up because the same force acts over less space.

The Pascal is named after the French scientist Blaise Pascal. You might also see pressure measured in other units like atmospheres or millibars, but in JAMB, they're testing your knowledge of the SI standard unit, which is always the Pascal.

Pressure is the force acting on a surface area. The relationship between pressure, force, and area is expressed as pressure equals force divided by area. When force increases while area stays the same, pressure increases. When area increases while force remains constant, pressure decreases. Think about walking on sand in Lagos—when you wear flat shoes, you sink deeply because your weight is concentrated on a small area, creating high pressure. But when you lie down on the same sand, your weight spreads over a larger area, producing low pressure, so you don't sink as much. This principle applies everywhere: sharp knife blades cut better than blunt ones because they concentrate force on tiny areas, creating enormous pressure. Understanding this relationship helps you solve countless UTME problems involving hydraulic systems, atmospheric pressure, and fluid mechanics.

A barometer measures atmospheric pressure, which decreases as you go higher. Since pressure drops predictably with altitude, you can use a barometer to estimate how high you are above sea level. At sea level, atmospheric pressure is about 760 mmHg, but on top of a tall mountain or building, it's noticeably lower. If you know the pressure reading and how pressure changes with height, simple calculations give you your altitude.

Think of climbing Obudu Mountain in Cross River State. Your barometer reading at the base differs significantly from the reading at the peak, allowing you to calculate the mountain's height without a measuring tape.

The relationship between pressure drop and altitude is roughly linear for heights within the troposphere, making this method practical for everyday use. This works because air gets thinner as altitude increases.

Pressure is simply force spread over an area. When you push with the same force but over a smaller area, you create more pressure. Think of it like this: when a lady wears high heels, her feet hurt the ground more than when she wears flat shoes, even though her weight is the same. The high heel concentrates all her weight into a tiny area, creating enormous pressure.

The relationship between pressure, force, and area is straightforward: pressure equals force divided by area. If you increase force while keeping area constant, pressure increases. If you decrease the area while keeping force the same, pressure also increases dramatically. A thumbtack works this way—the sharp point has tiny area, so even light pressure pushes it into wood.

In Nigeria, when a lorry parks on soft ground, it sinks deeper than a car because the lorry's greater weight (force) creates higher pressure on the soil.

Pressure in fluids increases as you go deeper because there's more fluid above pushing down on you. Think of it like this: when you dive into a swimming pool, your ears feel more uncomfortable the deeper you go. That uncomfortable feeling is increasing pressure from the water above.

The relationship is straightforward. Pressure depends on depth and density of the fluid. In Nigeria's Lagos lagoon, a diver at 10 metres deep experiences much greater pressure than at 2 metres because more water sits above them. A denser fluid like seawater creates more pressure than fresh water at the same depth.

The formula you need is P = ρgh, where P is pressure, ρ (rho) is density, g is gravity, and h is depth. This tells you that pressure increases directly with both density and depth.

The principle of transmission of pressure states that pressure applied to a fluid in a closed container spreads equally in all directions. When you squeeze a liquid or gas trapped in a sealed space, the pressure you create pushes outward uniformly on every wall.

Think of a hydraulic car jack used in Nigerian mechanic workshops. When the mechanic pumps oil into the sealed cylinder, the pressure from that pump transmits equally throughout the oil. This equal pressure then pushes the large piston upward with tremendous force, lifting the heavy vehicle. The small input force creates a large output force because pressure distributes evenly.

This principle also explains how your bicycle brake system works. Squeezing the brake lever creates pressure in the brake fluid that transmits equally to all wheel brakes simultaneously, stopping you safely.

Pressure in liquids is the force that liquid exerts on surfaces it touches. When water fills a container, it pushes on the walls and bottom because of its weight. The deeper you go into the liquid, the greater the pressure becomes. This happens because more liquid sits above, pressing down with greater force.

Think about a borehole in your village. The pressure at the bottom where the pump sits is much stronger than near the top. This is why boreholes need stronger materials at the base. The formula is Pressure = ρgh, where ρ is the liquid's density, g is gravity, and h is the depth.

Liquids push equally in all directions at the same depth—this is Pascal's principle. Understanding this helps solve problems about dams, tanks, and water systems common in Nigeria.

Pressure is simply the force pushing on a surface divided by the area it covers. Think of it like this: when you stand on soft ground with flat feet versus standing on one leg, you sink deeper on one leg because the same weight (force) is concentrated on a smaller area. Pascal's principle states that when pressure is applied to a liquid in a closed container, that pressure spreads equally in all directions. This principle explains how hydraulic systems work—like the brake system in your father's car or the hydraulic jack used to lift vehicles in mechanic shops across Nigeria. When the driver presses the brake pedal, the force creates pressure in the brake fluid, and this pressure transmits equally through all the pipes to push brake pads against the wheels simultaneously.

Pressure in liquids happens because liquid molecules have weight and they push downward on everything below them. Think of it like this: when you dive deep into a swimming pool, your ears hurt because the water above you is pushing down with more force. This pushing force creates pressure, and it increases as you go deeper because more water sits on top of you.

The pressure at any depth depends on three things: how heavy the liquid is, how deep you go, and gravity. A practical Nigerian example is our boreholes and water tanks. The water pressure at the bottom of a full overhead tank is much stronger than at the top, which is why taps at ground level often have weaker water flow than those closer to the tank's height.

Density tells you how tightly packed matter is in a substance. It's the mass of an object divided by its volume, measured in kg/m³. Relative density, however, compares a substance's density to the density of water. Water has a density of 1000 kg/m³, so relative density is simply a substance's density divided by water's density. This means relative density has no units—it's just a number.

Think of it this way: if you have palm oil, its density is about 920 kg/m³. To find its relative density, you divide 920 by 1000, getting 0.92. This tells you palm oil is 0.92 times as dense as water, which is why it floats on water. Metals like iron have relative densities greater than one, meaning they sink.