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These two short online tutorials discuss how the earth rotates and then the earth's revolutions.

In the first URL, the YouTube video explains why earth has spring, summer, autumn and winter seasons. The second URL summarizes the key takeaway points.

Part 1: Equivalent fractions and the simplest form of a fraction
Part 2: Examples of equivalent fractions
Part 3: Common mistakes and misconceptions

How to solve for the horizontal displacement when the projectile starts with a horizontal initial velocity. We also explain common mistakes people make when doing horizontally launched projectile problems.

Part 1: Proper, improper and mixed fractions
Part 2: Examples of proper, improper and mixed fractions
Part 3: Common mistakes and misconceptions

• Predict, qualitatively, how an external force will affect the speed and direction of an object's motion.
• Explain the effects with the help of a free body diagram.
• Use free body diagrams to draw position, velocity, acceleration and force graphs and vice versa.
• Explain how the graphs relate to one another.
• Given a scenario or a graph, sketch all four graphs.

Use two methods to find the sum of mixed numbers: improper fractions and mixed numbers