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e.g., Find r,

the last digits are meaningless

because one dimension is measured as 5.5”

• Basic rules of calculations for engineering,

1.To count the number of significant figures, don’t count zeroes at the start of the number, but do count zeroes at the end.

2.When doing calculations, the number of significant figures should be considered. All numbers and results should have the same number of significant figures, or one/two extra for more accurate numbers.

3.Generally, the final result must have at most the same number of significant figures as the least significant number.

4.Typical engineering numbers have 3 or 4 significant figures as they are determined from real systems experimentally.

5.Be aware that different operations may increase or decrease accuracy.

6.Engineers use engineering notation for numbers in exponential form, for example 0.0003

should be 0.3x10-3 not 3x10-4.

2.5 FUNDAMENTAL THEORIES

2.5.1 Newton’s Laws

• The fundamental laws,

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1.Inertia - a particle at rest, or moving along a path will continue to sit still, or move in the same direction with a constant velocity, as long as there are no unbalanced forces applied.

v

2.Acceleration - The application of a force to a particle will result in an acceleration in the direction of the force, and proportional to the force. The action and reaction forces balance to zero.

F

a small rocket motor at the side, is used for steering

rocket flying through space accelerates sideways when steering motor fired.