Introduction to Pressure & Fluids - Physics Practice Problems

Summary

This lesson covers the concept of pressure, explaining that pressure is the force applied over an area, measured in Pascals. It details the relationship between force, area, and pressure, emphasizing that pressure increases with force and decreases with area. The video includes examples, such as calculating the pressure exerted by a book and by water in a container. Additionally, it explains how to calculate pressure in fluids using density and depth, with the formula involving the fluid's density, gravitational acceleration, and height. This provides a clear understanding of how pressure works in different contexts.

Takeaways

• 😀 Pressure is defined as force divided by area.
• 😀 The standard unit of pressure is pascals (Pa), where 1 Pa = 1 N/m².
• 😀 1 kilopascal (kPa) equals 1,000 pascals, and 1 atmosphere (atm) equals 101.3 kPa.
• 😀 When force is applied over a larger area, the pressure decreases, and when force is increased, the pressure increases.
• 😀 Pressure is directly proportional to force and inversely proportional to the area on which the force is applied.
• 😀 Example 1: If 100 newtons of force are applied to 1 square meter, the pressure is 100 pascals. If the area doubles to 4 square meters, the pressure drops to 25 pascals.
• 😀 To calculate pressure exerted by an object, use the formula: pressure = force / area.
• 😀 Example 2: A 15 kg block with dimensions 70 cm by 40 cm exerts a pressure of 525 pascals on a table.
• 😀 To calculate the pressure exerted by a fluid, use the formula: pressure = (density × gravity × height) / area.
• 😀 Example 3: The pressure exerted by water in a container with a height of 6 meters is 58,800 pascals.
• 😀 Specific gravity is the ratio of the density of a substance to the density of water. The pressure exerted by a fluid at a specific depth can be calculated using this relationship.

Q & A

What is the formula for pressure in physics?

Pressure is defined as force divided by area. The formula is: Pressure = Force / Area.

What is the standard unit of pressure in physics?

The standard unit of pressure is the pascal (Pa). One pascal is equivalent to one newton per square meter.

How does increasing the area affect the pressure exerted by a force?

If the area increases while the force remains the same, the pressure decreases. Pressure is inversely related to the area over which the force is applied.

How does increasing the force affect the pressure exerted?

If the force increases while the area remains the same, the pressure increases. Pressure is directly related to the force applied.

What is the pressure exerted by a 15 kg block resting on a table with a 70 cm by 40 cm base?

The pressure exerted by the block is calculated as the force (mg) divided by the area. The force is 147 newtons, and the area is 0.28 square meters. So, the pressure is 147 N / 0.28 m² = 525 pascals.

How do you calculate the pressure exerted by a fluid on the bottom of a container?

The pressure exerted by a fluid on the bottom of a container is calculated using the formula: Pressure = Density × Gravitational acceleration × Height of the fluid.

What is the pressure exerted by water on the bottom face of a container with dimensions 4m by 5m by 6m?

The pressure is calculated using the formula: Pressure = Density × Gravitational acceleration × Height. Given that the density of water is 1000 kg/m³, the gravitational acceleration is 9.8 m/s², and the height is 6 meters, the pressure is 58,800 pascals.

How do you calculate the pressure exerted by a fluid at a given depth?

The pressure exerted by a fluid at a certain depth is calculated using the formula: Pressure = Density × Gravitational acceleration × Depth.

What is the relationship between specific gravity and the density of a fluid?

Specific gravity is the ratio of the density of a substance to the density of water. To find the density of a fluid with a known specific gravity, multiply the specific gravity by the density of water.

What is the pressure exerted by a fluid with a specific gravity of 1.7 at a depth of 50 meters?

First, calculate the density of the fluid by multiplying the specific gravity (1.7) by the density of water (1000 kg/m³), giving a fluid density of 1700 kg/m³. Then, use the formula Pressure = Density × Gravitational acceleration × Depth. The pressure is 1700 × 9.8 × 50 = 249,900 pascals, or 249.9 kilopascals.