Page 216 - Physics

Physics for Secondary Schools
Exercise 9.2
Answer all questions (where
necessary use g = 10 N/kg).
1. State fi ve forms of energy.
2. (a) Determine the potential energy
possessed by a particle of mass
0.2 kg resting on a tabletop 1.6
m above the fl oor.
(b) Amina has a mass of 80 kg. If
she runs at a speed of 10 m/s,
calculate her kinetic energy.
3. A stone of mass 10 kg is dropped
down to the ground from the roof of
a building 20 m high. If it hits the
ground with a velocity of 20 m/s,
determine its:
(a) kinetic energy.
(b) change in potential energy.
4. Find the elastic potential
energy stored in the spring
with k = 100 N/m when the spring
is stretched to 0.5m from its natural
length of 1 m.
5. A spring with spring constant
k = 100 N/m was initially compressed
by x = 0.4 m, after that, it was
released and stopped at x = 0.2 m
compression. Find the work done by
the restoring force in this process.
210
Physics Form 1 Final.indd 210
Acti vity 9.2
Aim: To demonstrate the
existence of potential
energy and kinetic energy.
Materials: Helical spring, thread,
retort stand, and 100 g mass
Procedure
1. Clamp a helical spring on a retort
stand.
2. Attach a 100 g mass to the bottom
of the spring.
3. Pull the mass downward for about
5 cm then release it.
4. Observe the up and down motion of
the mass.
Questions
(a) What form of energy did the mass
have at the initial rest point?
(b) Explain the changes in energy as the
mass moves up and down.
When a helical spring is set in motion, the
mass possesses kinetic energy. Initially, it
had potential energy due to its position.
A mass at rest possesses potential energy
only.
Task 9.1
1. List down all forms of energy that
you know.
2. Discuss and illustrate the importance
of the forms of energies you have
listed.
Student’s Book Form One
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