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UNIT II - FORCES
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Specific Objectives
Students should be able to:
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Explanatory notes
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Suggested Practical Activities
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1
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Discuss the principles of forces;
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Action/reaction principle applied in space transport;
the forward motion of jet aircraft; relationship between shape of wings of planes and birds and lift forces they experience while moving through the air;
motion of vehicles, road surfaces and tyres;
the effects of wind speed and wind currents on the motion of aircraft
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Action-reaction principles, for example, releasing an inflated balloon, using a pair of spring balances; demonstrate by blowing over strips of paper held at one end; use of ball on different surfaces;
use of paper aircraft models and fan)
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2
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describe gravity as a force;
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Definition, centripetal and centrifugal forces;
the relationship between height of the center of gravity of an object and its stability;
the implications for stability on the loading of vehicles in relation to their center of gravity;
reasons for maximum loading capacity and tare
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Show how an object can escape the pull of gravity;
throwing a ball up and observing its motion;
releasing objects attached to suspended spring/ not attached to anything;
using models to demonstrate how an object can escape the pull of gravity if given enough kinetic energy by whirling around the head of a rubber band attached to a weak thread
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3
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define center of gravity |
Conditions for equilibrium under parallel forces;
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Use of cardboard cut-outs of triangles, rectangles, circles and irregular shapes to arrive at the approximate position of the center of gravity of objects of simple shapes;
items such as lead pencils, rulers and solids with regular shapes should be used to locate the center of gravity.
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4
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define stable and unstable and neutral equilibrium; |
The characteristics of space and how problems affecting human life in space might be overcome.
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Use of small ball, a concave/convex dish, or a cone shaped object and a flat surface to demonstrate the three types of equilibrium; use of rule suspended by a spring balance and kept horizontal by known suspended weights to show that:
- the sum of the forces in one direction must equal the sum in the opposite direction
- the sum of the clockwise moments about a pivot must equal the sum of anti-clockwise movements
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| 5. |
explain the term “satellite” |
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Use of models to show how the planets orbit the sun |
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this is really helpful