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Groups can assess each other’s dynamometers by determining how effectively they work. Compile a matrix in which the criteria that are to be assessed, as well as the criteria describers, are given. Allow the learners to join you in deciding about this, so that they will know exactly how the dynamometer will be assessed before the start of the project.
The weights of objects of which the weight will be determined will depend on the size of the objects that are used.
Conclusion
The greater the mass of the object, the greater the earth’s gravitational force upon it.
Let us test our knowledge:
(a) A force is exerted on an object, for example by pulling or pushing it.
(b) Newton (N).
(c) Dynamometer/spring-balance.
(d) E.g. 60 kg _______mass; then your weight is ± 600N seeing that 1 kg has the weight of ± 10N.
(e) Weight is the gravitational force of the earth on an object.
(f) Electrostatic force
Gravitational force
Magnetic force
(g) Tensile force
Momentum (thrust)
Rotational force/torque (torsion)
(h) A force can make an object rotate.
A force can halt a moving object.
A force can change the speed of an object.
A force can change the shape of a moving object.
A force can change the direction of a moving object.
(i) c
(j) Rotation
Build your own dynamometer
Requirements:
Step 1: Glue the white paper to the wood.
Step 2: Screw the screw in at the top of the plank.
Step 3: Suspend the elastic band from the screw and clamp the plank in the stand.
Step 4: Use the hammer and nail to pierce four holes at equal distances along the edge of the tin lid.
Step 5: Attach four pieces of string (each ± 150 mm long) to the lid, by tying them through the holes. Tie the four loose ends of string to another length of string (± 300 mm long). Then attach this longer length of string to the elastic band.
Step 6: Make a mark on the paper immediately below the elastic band. This is the O position.
Step 7: Now place the mass pieces (to a total of 102 grams) on the lid. Mark the new position of the elastic band as “1”.
Step 8: Repeat step 7, increasing the mass of the mass pieces as you proceed, until you have marked 5 graduations on the paper. Avoid putting too much strain on the elastic band – if it is stretched too far, it might snap.
You have now built a simple dynamometer calibrated in Newton. 1 N is equal to ± 102 g. One kilogram is therefore equal to approximately 10 N.
Use this dynamometer or another spring balance to determine the weight of the following objects:
| OBJECT | WEIGHT IN N |
| one pen | ______________________N |
| five such pens | ______________________N |
| your shoe | ______________________N |
| both your shoes | ______________________N |
| an object of your choice | ______________________N |
Complete:
Deduction:
The greater the___________________________________________, the greater the
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