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This text is meant to accompany class discussions. It is not everything there is to know about uniform circular motion. It is meant as a  prep for class. More detailed notes and examples are given in the class notes, presentations, and demonstrations (click here.)

Click for the questions that go with this reading
Ratio Styled Problems

Sometimes a question comes up where there are very few numbers, but still require an equation to solve. These problems contain words and phrases like, double, half, triple, factor of... These problems can be solved by ratios.

Below is an introduction to how this is done utilizing Newton's second law of motion.


  1. A runner is competing in a piggy-back race with his friends. He is applying an unbalanced force as he accelerates from rest. The runner drops his passenger from his back and now moves with the same force as before but 1.5 times his earlier acceleration. By what factor did his mass change when he shed his passenger?
  2. A truck is moving down the road when an alien ray changes its mass by a factor of 2.4 and the truck responds by producing an acceleration that changes by a factor of 0.6. By what factor of change did the truck’s force change? If the truck’s original force was 9000N then what is the trucks new force after the alien ray?


See the video solution below.

by Tony Wayne ...(If you are a teacher, please feel free to use these resources in your teaching.)

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