[Physics Class Notes] on Tide Pdf for Exam [2024]

Tides are the rise and fall of sea levels caused by the combined effects of the Moon and Sun’s gravitational forces, as well as the Earth’s rotation.

Tides adjust the depth of the sea and create oscillating currents called tidal streams, making tide prediction crucial for coastal navigation.

The intertidal zone, which is a stretch of seashore that is underwater at high tide and exposed at low tide, is a significant ecological product of ocean tides.

The changing ocean tides created at a given location on the Earth is the product of the Moon’s and Sun’s changing positions relative to the Earth, as well as the effects of the Earth’s rotation and the local bathymetry.

Despite the fact that the Sun’s gravitational force on the Earth is about 200 times greater than the Moon’s, the Moon’s tidal force is about twice as large as the Sun’s. This is because the tidal force is proportional to the gradient of a gravitational field, not to its strength.

Since the Sun is about 400 times farther away from the Earth than the Moon, the gradient of the Sun’s field, and thus the tidal force created by the Sun, decreases more rapidly than the field strength with distance from the source.

Due to a variety of variables that decide the lunitidal interval, tides differ on timescales ranging from hours to years. Tide gauges at fixed stations monitor water level overtime to make reliable records. Variations produced by waves with intervals shorter than minutes are ignored by gauges. These figures are compared to the reference (or datum) level, which is commonly referred to as mean sea level.

While sea tides are the most common cause of short-term sea-level fluctuations, storm surges can also be caused by forces such as wind and barometric pressure changes, particularly in shallow seas and near coasts.

Why Tides Occur?

[]

Earth and its water bulge out on the side nearest to the moon and the side farthest from the moon due to the tidal force. High sea tides cause these water bulges.
Every day, the area of the Earth moves through both of these bulges as the Earth rotates.
A high tide occurs while you are in one of the bulges.
A low tide occurs when you are not in one of the bulges.
On most days, this pattern of two high tides and two low tides happens in most of the world’s coastlines.
Tides are just all about gravity, and the moon’s gravity is what causes the daily tides.
The moon’s gravity pulls on various parts of our earth as it rotates.
Even though the moon is just around 1/100th the mass of Earth, it has enough gravity to shift objects around because it is so close to us. Even the land is pulled by the moon’s gravity, but not enough for us to notice.
Everyone is bound to notice when the moon’s gravity pulls on the water in the oceans. Water moves far more easily than air, and it likes to bulge in the direction of the moon. This is referred to as the tidal force.
The water on the moon’s side still tries to bulge out into the moon due to the tidal force. A high tide is what we term this bulge. A high tide can occur as your part of the Earth rotates into this bulge of water.
The Earth is not coated in an equal layer of water like a global ocean. There are seven continents, and land is a major obstacle. The continents obstruct the water’s ability to pursue the moon’s pull perfectly. As a result, the difference between high and low tide in some areas is minimal, while in others, the difference is significant.
The moon’s gravitational force is strongest on the side of Earth that faces it directly. On that side, the water is firmly pushed in the direction of the moon.
The moon’s gravitational force is weakest on the side of Earth closest to the moon. The gravitational force of the moon on the whole planet is roughly averaged at the Earth’s centre.
We deduct the average gravitational pull on Earth from the gravitational pull at each position on Earth to get the tidal force, which is the force that causes the tides. The Earth is stretched and squashed as a result of the tidal force. The two tidal bulges are caused by this.
Since the Earth’s surface rotates around each of the bulges once a day, there are two high tides and two low tides in a single day.
Tides are caused by the Sun in the same way as the moon does, though they are smaller.

[]

When the earth, moon, and sun align, as they do at full and new moons, the lunar and solar tides strengthen each other, resulting in more intense tides known as spring tides.
When the lunar and solar tides oppose each other, the outcome is neap tides, which are unusually small tides.
Every two weeks, there is a new moon or a full moon, so high spring tides occur frequently.
The water level is also affected by wind and weather patterns. Strong offshore winds will push water away from coastlines, causing low tides to be exaggerated. Water can be pushed towards the shore by onshore waves, making low tides less visible.
Sea levels can be pushed down by high-pressure weather systems, resulting in lower tides. Tides that are much higher than expected can be caused by low-pressure systems brought on by powerful storms and hurricanes.

Types of Ocean Tides

In this tide information, we will learn about different types of tides and the regions where they occur.

1. Semi-Diurnal Tides

Every day, a semi-diurnal tidal cycle has two almost identical high tides and two low tides. The time between high and low tides is approximately 12 hours and 25 minutes. The Indian Ocean is home to the most Semi-Diurnal Tides. The Eastern African Coast and the Bay of Bengal are two other common coasts with semi-diurnal tides.

2. Diurnal Tides

There are four tides in a day of diurnal tides. The sun produces two tides, and the moon produces two. Springtide is a particularly high tide brought about by the Sun’s complementary position in relation to the moon. It’s worth noting that the Syzygy occurs when the Sun, Moon, and Earth are all in the same line. There are two forms of syzygy:

When the moon and the sun are on the same side, it is called a conjunction.

When the moon and the sun are on opposite sides, it is called opposition. The magnitude of the tide would be the same in all of these situations.

3. Mixed Tides

The mixed tidal cycle, or simply mixed tide, is formed by a tidal cycle of two unequal high and low tides. There are semi-diurnal and diurnal oscillations in this tidal cycle. It can be found all over the Gulf of Mexico and the Caribbean Sea. Mixed tides can also be found along the Brazilian coast in the southeast.

4. Spring Tides

When the sun and the moon are in alignment, spring tides form, pulling the ocean surface in the same direction. A spring tide occurs as high tides are higher and low tides are lower. It happens twice in a lunar month. The name King Tide has also been given to it.

5. Neap Tides

The spring tide is followed by the neap tide, which happens seven days later. The fact that the sun and the moon are at a right angle to each other is the most noticeable feature. The first and last quarters of the moon are when this tide happens. The moon’s gravitational pull and subsequent oceanic bulge are cancelled out by the sun’s gravitational pull and resulting oceanic bulge. In addition, in comparison to spring tides, neap tides have lower high tides and comparatively higher low tides.

[]

Characteristics of Tides

Flood Tide – The sea level can increase for a period of many hours.
High Tide – This is when the water level reaches its highest point.
Ebb Tide – This is a point in which the sea level continues to fall for a period of several hours.
Low Tide – When the seawater level begins receding, it is called a low tide.

Tides in Power Generation

Tidal energy can be extracted in two ways by incorporating a water turbine into a tidal current or by constructing ponds that release/admit water through a turbine.
In the first instance, the sum of energy is completely dictated by the timing and magnitude of the tidal current. However, since the turbines will block the ship’s passage, the best currents could be inaccessible.
In the second, impoundment dams are costly to construct, natural water cycles are interrupted, and ship navigation is hampered. With multiple ponds, however, power can be produced at specific times.
Aside from environmental concerns, engineering problems include merely surviving corrosion and biological fouling.
Proponents of tidal power argue that, unlike wind power, generation levels can be reliably predicted, with the exception of weather effects.
While some generation is possible for the majority of the tidal cycle, turbines lose efficiency as they operate at lower speeds.
The periods that high power generation is possible are limited because the power available from a flow is proportional to the cube of the flow speed.

Importance of Tides

During ebb tides, fishes will gather in groups. Commercial fishermen learn to fish at peak concentration levels and follow the tides to increase their economic investment and make better use of their time. Ebb tides are also good for recreational fishing since the concentrations of smaller fish attract the larger trophy fish. Tides have an effect on other facets of ocean life, such as fish and ocean plant reproduction. Tidal waves carry floating plants and animals between spawning areas and deeper waters. The tides assist in the removal of toxins and the circulation of nutrients that ocean plants and animals need to live.
The coastal zone is home to crabs, mussels, snails, seaweed, and other edible marine life. Tiny fish and sea vegetables can be found in small tide pools. Sealife in these areas is often harvested for food. These diverse and plentiful species would perish if the tides were not washed on a regular basis, and food supplies would be depleted.
The depth and currents in and around coastal areas are affected by tides. In certain places, ships can need to cross the seas during high tide to avoid running aground. When determining the best time to fly, pilots consider the water level, channel width, and water flow direction. To get tall loads under bridges, pilots can choose to fly when the tides are at their lowest. Tidal flows can aid or obstruct a ship’s progress in the water. The current can be used by pilots to get the craft where it wants to go. The efficiency of marine and inland shipping can be improved by having a detailed understanding of how tides influence navigation and how to use tides in navigation.
The weather is affected by tidal waves and tides, which churn up the ocean waters. Tides and tidal currents combine arctic water, which can’t absorb much light, with warmer topic water, which can. The stirring creates more stable and habitable climate conditions, as well as balancing global temperatures.
Every 24 hours, there are two high tides and two low tides. The predictability of the tides, as well as the rapid movement of water during the inflow and outflow, will provide a renewable energy source for coastal communities. Hydroelectric plants can use the flow of water in the same way as rivers do.

Conclusion

Understanding the gravitational force of the Sun and Moon will help us understand how tides work. The gravitational force between these bodies is determined by their mass and the distance between them. That the Sun is far further away from the Earth than the Moon. As a result, the Earth’s gravitational force is weaker than the moon’s. As a result, the tide’s magnitude is determined by the moon. It is commonly assumed that the gravitational pull only affects water bodies, but this is not the case. The gravitational pull affects both land and water bodies. The impact of gravitation on water bodies is greater since the relative pull of the ground is less than that of water.