Page 220 - Physics

Physics for Secondary Schools

The total energy is equal to the KE. At points like B, between the highest and the lowest
points, total energy is the sum of KE and PE.

Transducer
A device used to convert one form of energy to another is called a transducer. Table 9.2
shows some transducers and the corresponding energy transformation.

Table 9.2: Transducer and the respective energy transformation

Transducer Energy conversion process
Bulb Electric energy Heat energy Light energy
Generator Mechanical energy Electrical energy
Motor Electrical energy Mechanical energy
Solar panel Solar energy Electrical energy
Battery Chemical energy Electrical energy
Heater Electrical energy Heat energy
Microphone Electrical energy Sound energy

Example 9.9 Rearrange the equation to get v;
At its highest point A in Figure 9.22, a v = 2gh
pendulum of mass 0.8 kg is 1.2 m above the
equilibrium point. What will be its velocity v = 2 × 10 m/s × 1.2 m
2
as it swings through its lowest point?
∴v = 4⋅9m/s.

Therefore, the velocity of the
Highest
point A pendulum is 4.9 m/s.

1.2 m
Uses of mechanical energy
Lowest point Mechanical energy enables objects to
Figure 9.22 apply a force on other objects to cause
Solution displacement and hence do useful work.
Given data For a car, truck, train, or aeroplane to move,
mechanical energy is needed. Electricity
Height, h = 1.2 m, Mass, m = 0.8 kg, is normally obtained by dynamos which
g = 10 N/kg are driven by some forms of mechanical

Due to the law of conservation energy. Juicer uses mechanical energy to
of energy, maximum KE at squeeze fruits.
lowest position = maximum Task 9.2
PE at the highest position
1 mv = mgh Discuss the role of mechanical energy
2
2 in your daily life.

214
Student’s Book Form One

Physics Form 1 Final.indd 214 16/10/2024 20:58