Force and Pressure

We use force daily.

Force is a push or pull on an object.

vts strength. When forces act in the same direction, their magnitudes add. When they act in opposite directions, their magnitudes subtract.

Force depends on magnitude and direction, making it a vector quantity.

Balanced and Unbalanced Forces

Balanced forces are equal in size but opposite in direction, resulting in no change in motion.

Unbalanced forces cause a change in motion and are unequal in magnitude.

Types of Forces

Contact forces require physical contact, while non-contact forces do not.

I. Contact Forces

Examples of contact forces:

• Muscular Force: Force exerted by muscles.

• Frictional Force: Opposing force between surfaces in contact.

• Mechanical Force: Force exerted by machines.

II. Non-Contact Forces

Examples of non-contact forces:

• Gravitational Force: Attraction between objects with mass.

• Electrostatic Force: Force between charged particles.

• Magnetic Force: Force exerted by magnets.

Pressure

Pressure is force per unit area.

Pressure = \frac{Force}{Area}

The S.I. unit of pressure is pascal (Pa) or Nm^{-2}.

Factors affecting pressure:

1. Pressure is directly proportional to force.

2. Pressure is inversely proportional to area.

Some Applications of Pressure

• Sharp knives cut easily due to small area.

• Wide foundations reduce pressure on the ground.

• Broad tires reduce pressure on the ground.

Forces in Solids, Liquids, and Gases

• Solids apply force downwards.

• Liquids apply force downwards and towards container walls.

• Gases apply force in all directions.

Pressure in Fluids (Liquids and Gases)

Fluids exert pressure on immersed bodies and container walls.

Factors Affecting Liquid Pressure

1. Greater density, higher pressure.

2. Greater depth, higher pressure.

3. Pressure is the same at the same depth.

4. Pressure acts equally in all directions in an enclosed liquid.

Pascal's Law

Pressure on an enclosed liquid is transmitted equally in all directions.

Applications of Pascal's Law

• Hydraulic press, brakes, and lifts.

Applications of Liquid Pressure in Our Daily Life

• Dams are thicker at the bottom.

• Sea divers need protective suits.

Atmospheric Pressure

Atmosphere exerts pressure due to its weight.

Atmospheric pressure decreases with height.