Physics:
Motion, Energy & Heat
Unit II(b) – Hagebusch
NEO A&M
General Physical Science – PHYS 1014
Work
• Work – _______________________________
_____________________________________
_____________________________________
work = _______ x ________
W = Fd
•
___________ – the SI base unit of measurement
for work
Work
• Example 3.1
– How much work is needed
to lift a 5.0 kg backpack to
a shelf 1.0 m above the
floor?
•
Example 3.2
• How much work is required
to lift a 50 lb box vertically a
distance of 2.5 ft?
Power
• Power – ______________________________
_____________________________________
power =
•
•
•
P=
Power is measured in units of ___________
1 hp = 550 ft∙lb/s
1 hp = 746 W (watts)
Power
W
t
P
Power
• Example 3.3
– An electric lift can raise a
500.0 kg mass a distance
of 10.0 m in 5.0 s. What is
the power of the lift?
•
Example 3.4
• A 150 lb person runs up a 15
ft stairway in 10.0 s. What is
the horsepower rating of the
person?
Potential Energy
• Energy – ______________________________
• ____________________ – energy associated
with an object position
– measured in joules ( J )
gravitational potential energy = ________ x ________
PE =
Potential Energy
• Example 3.5
– What is the potential
energy of a 2.14 kg book
that is on a bookshelf 1.0
m above the floor?
•
Example 3.2
• How much work can a 5.00
kg mass do if it is 5.00 m
above the ground?
Kinetic Energy
• Kinetic energy – ________________________
_____________________________________
– Ways to measure kinetic energy
1. The work _____________________________________
2. The work _____________________________________
• measured in joules ( J )
kinetic energy =
KE =
Kinetic Energy
• Example 3.7
– A 7.00 kg bowling ball is moving in a bowling lane
with a velocity of 5.00 m/s. What is the kinetic
energy of the ball.
• Example 3.8
– A 100.0 kg football player moving with a velocity
of 6.0 m/s tackles a stationary quarterback. How
much work was done on the quarterback?
Energy Flow
Resistance
Energy changes
1.
2.
3.
4.
5.
1.
2.
3.
4.
Work against _________
Work against _________
Work against _________
Work against _________
Work against _________
Increased ___________
Increased ___________
Increased ___________
Increased ___________
Energy Forms
• _____________________– the form of energy
associated with machines, objects in motion,
and objects having potential energy due to
gravity
– Ex: ______________________________________
• ______________________– energy stored in
the chemical bonds between atoms
– Released in a reaction know as ______________
– Ex: ______________________________________
Energy Forms
• _____________________–
the energy that travels
through space
– ______________________– all
forms of radiant energy that
travels in the form of a wave
Energy Forms
• __________________________– form of
energy from electromagnetic interactions
• __________________________– form of
energy derived from interactions of the
nucleus of atoms
Energy Conversion
Energy Conversion
• Potential energy can be converted to kinetic
energy
Example 3.9
• A 1.0 kg book falls from a height of 1.0 m. What is the velocity of the
book just as it hits the floor?
Example 3.10
• What is the kinetic energy of a 1.0 kg book just before it hits the floor
after a 1.0 m fall?
Energy Conservation
• ____________________________________
– Energy is neither created nor destroyed. Energy
can be converted from one for to another, but the
total energy remains constant.
Common Energy Sources
• Fossil Fuels
– Petroleum
– Coal
•
•
•
•
•
Moving Water
Nuclear
Solar
Wind
Geothermal
Energy Conservation
• U.S. Energy Information Administration
– The total primary energy use per capita in the
United States in 2003 was almost identical to that
in 1973
– Economic output (gross domestic product GDP)
increased 74%
– National energy intensity (energy used per unit of
GDP) fell 43%
– The energy savings was an estimated $430 billion
to consumers