Page 71 - Physics

Introduction to force

3. Record the weights of different objects in air.

4. Submerge the spring scale and attached objects in the water, making sure they
don’t touch the sides or bottom of the container.
5. Observe and record the readings on the spring scale for each object when submerged.

6. Present your results in Table 3.2.

Table 3.2

Object Spring reading Difference
In air In water

Questions
Discuss the differences in the weight measured when the objects are underwater
compared to the measurement in air.

Electromagnetic force (b) It is a central force (originates from

This is a force that includes both electric the centre or toward the centre);
and magnetic forces. It is relatively stronger (c) It is stronger than gravitational force;
than the force of gravity. (d) It is a long-range force (operates
over a very long distance);
The following are examples of situations (e) Its strength decreases as the distance
where electromagnetic forces are involved: between the objects increases; and
(a) In the formation of molecules of a (f) Its direction depends on the charges

substance. Atoms attract each other of the objects involved.
to form molecules. This is due to
electromagnetic forces.
Strong force
(b) If two parallel wires carrying This is a nuclear force that binds protons
current are placed near each other, and neutrons together to form atomic
the electromagnetic force acts on nuclei. The action of strong force results

the wires. in binding energy which can be felt
when splitting a large nucleus into small
Properties of electromagnetic force: fragments (fi ssion) or combining two

(a) It is either attractive or repulsive in or more nuclei to form a bigger nucleus
nature; (fusion), as illustrated in Figure 3.7.

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