The document summarizes force, work, energy, and their relationships. It defines force, describes the four fundamental forces (gravitational, electromagnetic, weak, and strong), and provides examples of contact and non-contact forces. It defines work as the product of force and displacement and provides examples of calculating work. It also describes different types of energy (potential, kinetic, chemical), how energy can transform between forms, and renewable and non-renewable sources of energy.

1. Force, Work & Energy
Marie Jessica B. Alumaga

2. Objectives:
• To cite examples of forces encountered in day
to day activities
• To describe and discuss the four fundamental
forces
• To state the scientific definition of work and
solve work problems
• To describe the different forms and
transformations of energy
• To explain how energy is related to work

3. Force
Force - push or pull
contact forces – exerted between objects
that are in close contact
noncontact forces – can be exerted
between objects that are not even
touching

4. Fundamental forces
• Gravitational force - affects anything that has mass
• Electromagnetic forces – exerted on charged objects
or magnetic objects
Like charges repel, unlike charges attract.
Like poles repel, unlike poles attract.
• Weak force – exerted between leptons and hadrons;
active only at distances less than 10-18 m
• Strong forces – acts only on hadrons; strongest of
the four but effective only at very short separations
(10-15m)

5. Work
Work - product of the force and displacement
(displacement – distance moved by an
object as a result of the force’s action)
- being done when all of the following
conditions are satisfied
a. A force is exerted on the object.
b. The object moves.
c. The motion is in the direction of
the force.

6. Work
Sample problem 1:
How much work is done when a 100-N cart is
pulled over a distance of 1 meter?
Given: F = 100N d = 1m
Find: W
Solution: W = Fd
W = 100N(1m)
= 100Nm or 100J

7. Work
To get the maximum amount of work , the
force must be parallel to the motion.

8. Work
The perpendicular component of the force
does no work, if there is no motion in that
direction .

9. Work: Sample problem 2
A box having 2 kg mass, under the effect of forces F1,
F2, and F3, takes distance 5 m. Which of the forces do
work? What is the work done by that force?
W3 = F3d = 30N(5m) = 150J

10. Power
Power – refers to the rate at which work is done
P = Wdone/time
Unit of power:
• joule/second (J/s) 1J/s = 1 watt (W)
• Horsepower (hp) 1hp = 746 W
- used to specify the power output of motors
and engine

11. Machine
Machine – a device that transfers a force from
its point of application to some other
point to where it is used
- may multiply force or distance or
simply change the direction of the
force

12. Simple Machines
Six Simple Machines
1. Lever – a rigid object that is free to rotate
about a fixed point called the fulcrum
2. Wheel and axle – rotating lever consisting of
a large wheel attached to a smaller
axle, which is just a rod or cylinder
3. Pulley – modified lever; grooved wheel that is
free to turn about an axle

13. Simple Machines
Six Simple Machines
4. Inclined plane – a flat surface with one end
placed higher than the other
5. Wedge – two inclined planes set back to back
6. Screw – an inclined plane that is wound
around a cylinder

14. Concept of Energy
Energy - capacity to do work
• If something has energy it can do work.
• If something can do work, then it has energy.
• Work and energy have the same unit, (joule,J)
• It cannot be seen but evidences prove its
existence.

15. Different Forms of Energy
Potential Energy (PE)
- stored energy due to the object’s position or
internal arrangement of molecules
Kinetic Energy (KE)
- energy of moving object

16. Different Forms of Potential Energy
1. Gravitational potential energy
- energy is due to the object’s position or height
from the earth
The higher the position, the greater is the
gravitational PE
2. Magnetic potential energy
- energy from magnets
3. Chemical energy
- energy due to the arrangement of the atoms and
molecules in matter

17. Different Forms of Kinetic Energy
1. Electrical Energy – due to the motion of charged
particles through conducting wires
2. Nuclear Energy – energy derived from the nuclear
reaction
nuclear fusion – nuclei join to form a nucleus
nuclear fission – nucleus is broken into smaller nuclei
3. Radiant Energy – energy transported by
electromagnetic waves
4. Thermal Energy - sum of the KE’s of the molecules
due to their linear motion

18. Energy Transfer
Heat can be transferred through
• Radiation – transfer by rays or
electromagnetic waves
• Conduction – transfer by direct contact
• Convection - transfer involving difference in
density

19. Energy transformation
Energy cannot be created nor destroyed, it
can only be transformed from one form to
another. (Law of Conservation of Energy)
• Electrical energy chemical energy
• Chemical energy electrical energy
• Radiant energy chemical energy

20. Sources of Energy
• Renewable sources
- energy sources that can be replenished
• Nonrenewable sources
- energy sources that has undergone long
process of formation

21. Sources of Energy – Renewable Sources
• Geothermal energy - heat energy from deep
within the earth
• Hydropower - energy from moving water
• Tidal energy - energy from the regular rise and
fall of sea water
• Wind energy - energy from wind mills
• Solar energy - energy rom the sun
• Biomass – energy resource that is derived from
plant or animal matter

22. Sources of Energy – Nonrenewable Sources
• Fossil fuels - derived from the remains of plants
and animals that died millions of years ago
petroleum – also called crude oil; complex
mixture of hydrogen and carbon
compounds
coal – most abundant and dirtiest fossil fuel
natural gas – mainly methane and the
cleanest of all the fossil fuels
• Nuclear energy – energy from fission or fusion
reaction

23. Problems Related to Energy
1. Combustion of fossil fuels release gases and solid
pollutants that are harmful to living and non-living things.
2. Nuclear energy production
a) release radioactive substances harmful to living things
b) waste disposal
c) poses risk of reactor accidents
d) causes thermal pollution
3. Tidal and hydroelectric dams create ecological froblems.
4. geothermal energy emits H2S

24. Energy Utilization and Consumption
• All people are users of energy.
• Energy sources are popularly used for the
generation of electricity
• Factors that will affect the selection of energy for
electricity include
- availability in the country
- cost of production
- availability of local manpower to make and
repair the plant
- ecological impact during extraction, utilization
and waste disposal

25. Energy conservation
- refers to the practice of extending the useful
life of the earth’s energy resources
- should be taught early in life
- influenced by the people’s attitudes, mores and
beliefs

26. Small things make a big difference.
MJBA

27. References
• McLaughlin, Charles W., Thompson, Marilyn, and
Zike, Dinah. (2012). Glencoe Physical Science.
McGraw-Hill Education
• Serway, Raymond A., Vuille, Chris and Faugnn,
Jerry S.(2009). College Physics (Volume 2) 8th ed.
Brooks/Cole Cengage Learning
• Tillery, Bill W. (2011). Physical Science McGraw-
Hill Publishing Co.