INTRODUCTION_TO_FORCES-summary

Introduction to Forces

• Forces are actions that can change the state of motion of an object.

• Allow for calculations in net forces.

• Represented visually in diagrams for clarity.

Physical Quantities

Base Quantities

• Defined independently and cannot be derived from one another.

  • Examples: Length, Mass, Time, Temperature, Electric Current.

Derived Quantities

• Defined in terms of base quantities through multiplication or division.

  • Examples: Speed (m/s), Volume (m³), Force (Newton, N).

Measuring Instruments for Base Quantities

Measuring Volume of Irregular Objects

Displacement Method

1. Fill graduated cylinder with water.

2. Note initial volume (V1).

3. Submerge object, note new volume (V2).

4. Calculate volume of object: Volume = V2 - V1.

Inference

• The water displaced equals the volume of the object.

• Archimedes' principle applies, demonstrating the relationship of volume between solid and liquid.

Temperature Conversion

Formulae

• Celsius to Kelvin: K = °C + 273.15

• Kelvin to Celsius: °C = K - 273.15

Example Problem

• Liquid oxygen boiling at -182.96 °C to Kelvin:

  • K = -182.96 + 273.15 = 90.19 K

Force

Definition

• A push or pull affecting an object.

Types of Forces

• Contact Forces: Requires physical interaction (e.g., friction, tension).

• Non-Contact Forces: Acts at distance (e.g., gravity, magnetism).

Effects of Forces

• Forces can change:

  • Shape (e.g., squeezing a sponge).

  • Direction (e.g., hitting a ball).

  • Motion (e.g., pushing a car).

Measuring Forces

Force Meter

• Also known as a Newton meter used to measure the size of a force.

Important Note

• Zero the meter to avoid systematic errors in measurement.

Resultant Force

• The sum of all forces acting on an object.

• If two forces act in the same direction, add them. If opposite, subtract them.

Calculating Net Forces

• Adding Forces: When in the same direction.

• Subtracting Forces: When in opposite directions.

Balanced vs. Unbalanced Forces

Balanced Forces

• Forces equal in size and opposite in direction.

• No change in motion.

Unbalanced Forces

• Non-zero resultant force causing change in motion (acceleration).

Free Body Diagrams

• Visual representation of forces acting on an object.

• Arrows indicate direction and magnitude of forces.

Gravitational Force

• Attraction experienced between masses.

• Gravity pulls objects towards each other.

Mass vs. Weight

• Mass: Amount of matter measured in kg.

• Weight: Force due to gravity measured in N (Weight = Mass x Gravitational Strength).

Friction

Definition

• Resistance that occurs between two surfaces in contact.

• Acts opposite to the direction of movement.

Effects of Friction

• Slows down motion, causes wear, and creates heat.

Situations with Friction

Beneficial

• Enables walking, holding, and controlling vehicles.

Non-Beneficial

• Causes wear and tear on machines and increased fuel consumption.

Methods to Reduce Friction

1. Make surfaces smooth (polishing).

2. Apply lubricants (oil, grease).

3. Use wheels or ball bearings.

4. Design with aerodynamics.

Non-Contact Forces

Magnetic Force

• Attraction or repulsion without physical contact.

• Used in applications such as electric motors and MRI machines.

Electrostatic Force

• Force between charged objects; can be attractive or repulsive.

Summary

• Forces, their types, and effects are crucial in understanding physical interactions.

• Being able to calculate, measure, and represent forces accurately is essential in physics.