types of energy sections 6.3-6.5. what is energy? energy is the ability to do work like work, energy...
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What is energy?
• Energy is the ability to do work
• Like work, energy is measured in joules (J)
• What are some examples of having or using energy?– A moving baseball– Combing your hair– Walking up the stairs
Different Forms
• There are different forms of energy.
• When you turn on a light, the room gets brighter.
• When you turn on your stereo, you hear sound.
Think of money…
• If you had $100, you can keep it…– In your wallet– In a bank account– In travelers checks– In gold and silver coins
• The same is true for energy!! It can be found in different forms.
Mechanical Energy
• Mechanical Energies include….– Potential Energy is energy that arises
because of an object’s position– Kinetic Energy is energy of motion
possessed by moving objects
• Mechanical Energy may be in the form of potential energy, kinetic energy, or both.
Potential Energy (PE)
• Even motionless objects can have energy… the energy is stored in the object.
• An apple hanging in a tree has potential energy because it has the ability to cause change, to fall to the ground.
• Stored energy due to a position is called potential energy (PE).
Elastic Potential Energy
• Elastic potential energy is energy stored by something that can stretch or compress such as a rubber band or a spring.
Chemical Potential Energy
• Energy stored in chemical bonds is called chemical potential energy.
• Chemical energy is stored in bonds that hold a molecule together and are released when the bond is broken.
Gravitational Potential Energy• The potential energy that is
easiest to visualize is gravitational potential energy.
• Gravitational potential energy (GPE) is stored by objects that are above the Earth’s surface.
• The amount of GPE depends on:– The mass of the object– The acceleration due to
gravity– The height above the
ground
Gravitational Potential Energy• To calculate the GPE of an object, we
use the following equation:
• PE = mass x gravity x height• PE = mgh• PE (J) = m (kg) x g (m/s2) x h (m)
Gravitational Potential Energy• Example• What is the gravitational potential
energy of a 1 kg ball as it sits at the top of a 1.5 m table? Remember gravity = 10 m/s2.
• m = 1 kg, g = 10 m/s2, h = 1.5 m• Find PE.• PE = m x g x h• PE = 1 kg x 10 m/s2 x 1.5 m• 15 J
Changing GPE
• The GPE of an object can be changed by changing the height of the object.
• When the height of the object is increased, the gravitational potential energy increases!!
Kinetic Energy
• Kinetic energy is energy in the form of motion.– Wheels spinning– A sprinting runner– A train moving
Kinetic Energy
• Kinetic energy depends on two quantities…– The mass of the moving object– The object’s velocity
Kinetic Energy
• The more mass an object has, the more kinetic energy it has.
• The greater an object’s velocity is, the more kinetic energy it has.
Kinetic Energy
• Which one has the most kinetic energy?
Velocity = 5 m/s
Mass = 500 kg
Velocity = 20 m/s
Mass = 500 kg
Kinetic Energy
• Kinetic energy is measured in joules (J)
• We use the following equation to calculate how much kinetic energy an object has:
• Kinetic Energy = ½ (mass) x (velocity)2
• KE = ½ m v2
• KE (joules) = ½ m (kg) x v2 (m2/s2)
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