Transcript What is Energy?

What is Energy?
• Energy is the ability to do work
 In other words, energy is transferred by a force moving an object through
a distance (Work = Force x Distance)
 Ability to cause change
 Can change itself or its surroundings
 Measured in Joules (J)
Energy & Work
• Work is the transfer of energy
Example: carrying your backpack up the stairs
Muscles receive
energy from the food
you eat
Energy in food comes from plants that have used
energy of sunlight, or animals that have eaten such
plants
The energy to do the work
comes from your muscles
You do work on the
backpack by lifting it
against the force of
gravity…which requires
energy
Kinetic Energy
• Energy of motion
• Depends on 2 factors:
Why was KE highest at bottom?
 Mass
 Speed (velocity)
1
𝐾𝐸 = 𝑚𝑣 2
2
What would happen to KE if we doubled the mass?
 KE would double
What would happen to KE if we doubled the speed?
 KE would quadruple
Calculating KE
• A .10 kg bird is flying at a constant speed of
8.0 m/s. What is the bird’s KE?
Potential Energy
• Potential energy is energy that is stored as a
result of position or shape
• Has the potential to do work
• 2 forms of potential energy
 Gravitational potential energy
 Elastic potential energy
Gravitational Potential Energy
• GPE depends on height, mass, and gravity
What happens to GPE the higher
the object is?
 increases
𝑃𝐸 = 𝑚𝑔ℎ
m= mass (kg)
g= gravity = 9.8 m/s2
h= height (m)
Usually relative to the ground or
surface object is usually on
PE depends on where you
are considering the
reference line to be
 Has to be relative to
something
Elastic Potential Energy
Potential energy of an object that is stretched or compressed
 Something is said to be elastic if it springs back to its original shape after it is
stretched or compressed
Forms of energy
Energy associated
with electric
charges
Mechanical
Associated with motion and
position of objects
• Sum of PE and KE
• Speeding trains, bouncing balls,
sprinting athletes
electromagnetic
electrical
Form of energy that travels
through space in the form of
waves
Forms of Energy
Thermal
Motion of the particles in matter
• Faster the particles are moving, more
thermal energy
• Slower they’re moving, less thermal
energy
nuclear
chemical
energy stored in chemical
bonds
Energy stored in
atomic nuclei
What are some forms of energy you
notice around the room?