D845: General Physics I

D845 is the lecture half of WGU's general physics pair. The guidebook describes fundamental concepts such as Newton's laws, forces, motion, energy, waves, electricity and magnetism, with real-world applications and introductions to relativity and quantum theory.

It appears in WGU's Science Education guidebooks. The usual difficulty is turning words into a diagram and an equation: students may know a formula but not when it applies.

What D845 Covers

The description also lists measurement, wave motion and centripetal forces.

Key Concepts Explained

Newton's Second Law

Net force equals mass times acceleration (F = ma). The key word is net: add all forces as vectors first.

Conservation of Momentum

In a closed system, total momentum before a collision equals total after. Momentum is mass times velocity and has direction.

Energy Transformations

Energy changes form but is not created or destroyed. Track kinetic, potential and thermal energy, and note that some becomes less useful as it disperses, which links to entropy.

Typical Assignments and How to Approach Them

The guidebook does not name assessments. These are the kinds of work the competencies suggest.

A Competency-by-Competency Study Approach

1. Forces, motion, momentum. Draw a diagram for every problem and practice vector addition.
2. Energy and entropy. Practice energy bar charts and explain what happens to energy in a process.
3. Electricity and magnetism. Learn charge, current, fields and the link between electric and magnetic effects.

A Problem-Solving Routine for Physics

Follow the same routine for each problem type.

Solving algebraically first makes errors easy to find and shows reasoning to an evaluator.

Frequent Physics Slips

• Forgetting a force in the free-body diagram.
• Using speed where velocity direction matters.
• Mixing kilograms with grams or meters with centimeters.
• Applying energy conservation when energy is lost to friction.
• Reporting an answer without its unit.

Worked Example: A Collision

A 1.0 kg cart moving at 2.0 m/s hits a stationary 1.0 kg cart and they stick together. Momentum before is 1.0 x 2.0 = 2.0 kg m/s. After the collision the combined mass is 2.0 kg, so the speed is 2.0 / 2.0 = 1.0 m/s.

Kinetic energy before is half of 1.0 x 2.0 squared, or 2.0 J. After it is half of 2.0 x 1.0 squared, or 1.0 J. Half the energy was transformed into other forms such as heat and sound. Explaining that difference is exactly the kind of reasoning that links momentum to energy.

Where Students Get Stuck

• Skipping diagrams. Most errors come from missing forces.
• Plugging into formulas blindly. Decide which principle applies first.
• Unit inconsistency. Convert to standard units before calculating.
• Sign and direction errors. Choose positive directions at the start.

Study Tips for D845

• Practice a fixed routine: diagram, knowns, unknowns, principle, solve, check.
• Check that answers are physically sensible.
• Explain concepts aloud, since you are training to teach.
• Pair each topic with a real-life example.

How We Help with D845

Send your notes and practice problems. A tutor can explain concepts, work through problems or review your written explanations. For lab writing, see our lab report guide.

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