Forces in Space Lecture Notes

Wednesday 2nd April 2025

Topic: Forces in Space

Learning Objective: Gravity

  • Page 80, question q: Calculate the weight of an adult who has a mass of 75kg.

    • Weight = mass \times gravitational \ field \ strength

    • Weight = 75 \ kg \times 10 \ N/kg = 750 \ N

Weight

  • Measured in Newtons (N).

  • The value changes when the object's location changes.

  • It is the total amount of force on an object due to gravity.

Mass

  • Measured in kilograms (kg).

  • The value does not change when the object's location changes.

  • The amount of matter an object is made up of.

Calculating Mass

  • Calculate the mass of a car that has a weight of 8500 N.

    • mass = \frac{weight}{gravitational \ field \ strength}

    • mass = \frac{8500 \ N}{10 \ N/kg} = 850 \ kg

Thursday 27th March 2025

Topic: Forces in Space

Learning Objective: Gravity

  • Page: 75

Gravity

  • Gravity is a force exerted by one object on another when they are near each other.

  • The Earth has a large mass compared with everything on it.

  • The Earth's gravitational field strength is larger than our own, so we don't notice the gravitational force that our own bodies exert.

Gravitational Field Strength of Earth

  • 10 Newtons per kilogram (10 N/Kg)

Mass

  • The amount of matter that an object is made up of.

  • SI unit: kg

  • Relationships:

    • weight = gravitational \ field \ strength \times mass

    • mass = \frac{weight}{gravitational \ field \ strength}

  • Example: If weight = 800N and gravitational field strength = 10,
    \frac{weight}{gravitational \ field \ strength} = \frac{800}{10} = 80

Weight

{gravitational \ field \ strength}_{earth} \times mass

  • Example:

    • 1.6 \times 80 = 128 \ N

Thursday 10th April 2025

Topic: Forces in Space

Learning Objective: Eclipse (Lunar and Solar)

  • Page: 223

Solar Eclipse

  1. Total Eclipse: Umbra

  2. Annular Eclipse: Antumbra

  3. Partial Eclipse: Penumbra

  • Umbra: The portion of the moon's shadow covers the sun completely.

  • Antumbra: The moon is completely in front of the sun but does not cover the sun fully; an outline of the sun can be seen.

  • Penumbra: Only a portion of the moon is in front of the sun.

Lunar Eclipse

  • Occurs when the moon passes through the Earth's shadow.

  • Types: Total eclipse, Partial eclipse

  • Annular eclipse as solar eclipse

Friday 04th April 2025

Topic: Forces in Space

Learning Objective: Tides

  • Page: 98

Tide

  • The change in depth of water (ocean).

  • High Tide

  • Low Tide

  • Tidal Range

What causes Tides?

  • The gravitational pull of the moon. Pulls the sea towards it.

  • Tidal force.

  • There is approximately a 6-hour difference between high and low tides.

  • Larger tidal force when the Earth, Sun, and Moon are in line (Eclipses).

Wednesday 26th March 2025

Topic: Solar System

Learning Objective: Forces in Space

  • Page: 76

Forces

  • Measured using a Newton meter.

  • Unit for force: Newton (N)

  • A force is a push or pull on an object; it causes it to speed up, slow down, or stay in place.

Examples of Forces

  1. Contact Forces:

    • Friction

    • Air resistance

    • Water resistance

    • Buoyancy

  2. Non-Contact Forces:

    • Gravity

    • Magnetism

    • Electrical forces

Friction

  • A push against a moving object.

  • A force that stops or slows us down.

Air Resistance

  • Is a type of friction that occurs between the air and another material.

  • Example: Force that acts on a parachute.

Water Resistance

  • Pushes against objects, making it hard for them to move through water.