Energy is the quantities property that must be

transferred to an object to do the action of

work.

Energy is the capability for doing work.

Work and Energy

The Work is the

combination between

Force and Energy

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Energy is the ability to do work

•Energy comes in different forms:

Heat (thermal)

Light (radiant)

Motion (kinetic)

Electrical

Chemical

Nuclear energy

Gravitational

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• Mechanical energy is the energy possessed by

an object due to its motion or its position.

• Radiant energy includes light, microwaves, radio

waves, x-rays, and other forms of

electromagnetic waves.

• Nuclear energy is released when heavy atoms in

matter are split up or light atoms are put

together.

• The electrical energy we use is derived from

other sources of energy.

More about Energy

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There are two types of energy:

1. Stored (potential) energy

2. Working (kinetic) energy

•Energy is a measurement of the ability to do work.

•It is not a material substance.

•Energy is never really destroyed. It is just transferred

from one form to another.

For example, the food a person eats contains

chemical energy, and a person's body stores this

energy until he/she uses it as kinetic energy during

work or movements.

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Work – Constant Force

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Work – Constant Force Lec.4

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Work – Examples Lec.4

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Work – Examples

Work – Constant Force - Summary Lec.4

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• Energy of motion is called kinetic energy.

• The kinetic energy of a moving object depends on

two things: mass and speed.

• Kinetic energy is proportional to mass.

Kinetic Energy ( KE )

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KE = 1 mv2

2

Speed (m/sec)

Mass (kg)

Kinetic Energy

(joules)

Kinetic Energy ( KE ) - Formula

• kinetic energy increases as the square of speed.

• If the speed of an object doubles, its kinetic energy

increases four times (mass is constant).

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1. Calculate ] the speed of an 8.0×104 kg airliner with a kinetic energy of

1.1×109J.

2. What is the speed of a 0.145 kg base ball if its kinetic energy is109 J ?

3. Two bullets have masses of 3.0 g and 6.0 g, respectively. Both are fired

with a speed of 40.0 m/s. a)Which bullet has more kinetic energy?

B)What is the ratio of their kinetic energies?

4. Two 3.0 g bullets are fired with speeds of 40.0m/s and 80.0 m/s ,

respectively. What are their kinetic energies? Which bullet has more

kinetic energy? What is the ratio of their kinetic energies?

5. A car has a kinetic energy of 4.32×105J when traveling at a speed of 23

m/s. What is its mass?

Kinetic Energy ( KE ) – Problems

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