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.