1. Work
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2. Work
• It is defined as the product of the force
applied upon an object and the distance that
the object is moved in the direction of the
force.

3. • For work to be done, two things must occur:
1. You must apply a force to an object.
2. The object must move in the same direction as the
force you apply.

4. • Example1:
A force of 12 Newton acts on an object over a
distance of 15 meter. What is the work in Nm?

5. Unit of Work
• Another common unit of energy is the calorie.
1 calorie (cal) is equal to 4.18 joules (J).
1cal = 4.18 J

6. Examples:
• Example2:
An object is pulled 4 m on a horizontal surface
by applying a force of 50 N. Calculate the work
done on the object.
• Example3:
A boy pushes a box for 50 m on a frictionless
surface and he does a work of 10000 J. Find the
force that he applies to the box.

7. Energy
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8. What is energy?
• It is the ability to do work.
• We do work by using energy, so we can say
that work and energy should have the same
units: joule (J).

9. TYPES OF ENERGY
• Potential Energy: It is the energy of an object
due to its position.
• By raising an object from the ground to a height h,
we change its position, by applying a force at list
equal to its weight. So we do work against the force
of gravity. The work done on the object is stored as
potential energy.

11. Example:
• A man lifts up a 4.5 kg box on to a table which
is 120 cm high. How much potential energy
does the box gain? (g= 10 N/kg)

12. • Kinetic Energy: It is the energy of an object
due to its motion.
• Kinetic energy (EK) of an object of mass m
moving at a speed v and is given as;

13. Example:
• A cyclist has a mass of 43 kg and his bicycle
weighs 7 kg. If the cyclist moves with a speed
of 4 m/s in the forest, what will his kinetic
energy be?

14. • Mechanical energy: It is the total amount of
potential and kinetic energy in a system.
Mechanical energy=potential energy + kinetic energy