taks review objective 4 the student will demonstrate an understanding of motion, forces, and energy
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TAKS ReviewTAKS ReviewTAKS ReviewTAKS ReviewObjective 4Objective 4
The student will demonstrate an The student will demonstrate an understanding of motion, forces, and understanding of motion, forces, and
energy.energy.
Transformation of Energy
• Energy comes in what forms?– Heat, chemical, mechanical, &
electrical
• Creating electricity from geothermal, wind, burning of fossil fuels, hydroelectric, nuclear, etc. by changing forms
• Law of Conservation of Energy—energy is neither created nor destroyed, it can change forms
• Potential– Stored energy based on position;
energy that can do work
• Kinetic– Energy of motion; energy doing work
Transformation of Energy
On the next slide, explain where the ball has potential and kinetic
energy. Also, where is kinetic energy the lowest and the
highest?
On the next slide, explain where the ball has potential and kinetic
energy. Also, where is kinetic energy the lowest and the
highest?
Newton’s Laws
• 1st – objects in motion stay in motion at a constant velocity and objects at rest stay at rest unless another forces acts on it
• 2nd – F=ma• 3rd – for every action, there is an
equal but opposite reaction
Balanced vs. Unbalanced
• Balanced forces result in…– Objects at rest staying at rest– Objects in motion stay in motion at a
constant velocity
• Unbalanced forced result in…– Resting objects caused to move– Objects in motion change their speed
and/or direction
Motion Terms• Force
• Motion
• Speed
• Acceleration
A push or pull on an object; has a size and directionA push or pull on an object; has a size and direction
Movement; change in an object’s position over timeMovement; change in an object’s position over time
Distance traveled over time; distance divided by timeDistance traveled over time; distance divided by time
Change in speed over time; change in velocity divided by time to make change; + (speed up) or – (slow down)
Change in speed over time; change in velocity divided by time to make change; + (speed up) or – (slow down)
Calculations• A car has a mass of 900 kg. It
travels 600 m in the same direction for 30 s at a constant speed. What is its speed?
• What is its acceleration?
Speed = d/t = 600 m/30 s = 20 m/sSpeed = d/t = 600 m/30 s = 20 m/s
Acceleration is a change in speed; since the car is traveling at a “constant speed”, its acceleration is zero.
Acceleration is a change in speed; since the car is traveling at a “constant speed”, its acceleration is zero.
Calculations
• A rock is thrown from a bridge 15 m above the river with a 2.5 N force. It has a mass of 0.5 kg. What is the acceleration of the rock?
F = ma
25 N = 0.5 kg x a
a = 25 N / 0.5 kg
a = 50 m/s2
F = ma
25 N = 0.5 kg x a
a = 25 N / 0.5 kg
a = 50 m/s2
REMINDER
1 N = 1 kgm/s2
Calculations• A Southwest airplane travels at a
rate of 7 km/min at a height of 18,000 m above the Earth’s surface. How long will it take to travel from Dallas to San Antonio which is 315 km away?
Speed = d / t
7 km/min = 315 km / t
t = 315 km / 7 km/min
t = 45 min
Speed = d / t
7 km/min = 315 km / t
t = 315 km / 7 km/min
t = 45 min
Calculations
• Your classroom is 4 m by 6 m and each desk is 1.5 m by 1 m. How much work would you have to do to move a desk 10 m if you apply a force of 20 N?
Work = Fd (force x distance)
Work = 20 N x 10 m
Work = 200 N·m
Work = Fd (force x distance)
Work = 20 N x 10 m
Work = 200 N·m
Simple Machines
leverlever
pulleypulley
screwscrew
wheel & axlewheel & axle
More machines…
inclined plane
inclined plane
wedgewedge
Waves
compression wavecompression wave
transverse wavetransverse wave
Wave parts
crestcrest
troughtrough
wavelengthwavelength amplitude
amplitude
More waves
• Number of waves that pass a given point per unit of time is frequency
• In sound, frequency is related to pitch– High frequency = high pitch– Low frequency = low pitch
Electromagnetic Waves• Transverse waves that travel through
space; radiant energy• The EM spectrum:
Ocean Waves• Caused by wind• Amplitude called “wave height”• As waves approach the shore,
wavelength decreases and wave height increases until it “breaks” as it nears the shoreline
Seismic Waves• Caused by earthquakes• Measured with seismographs• Move through the crust of the Earth• Primary (P), Secondary (S), and Surface or
Longitudinal (L) waves• P-waves are fastest and move in
compressions• L-waves are slowest and
move earth up and down
Seismic Wave
demo…
P waveP wave
S waveS wave
Surface waveSurface wave
Seismic Waves…
surface wavesurface wave
s-waves-wave p-wavep-wave
Wave ReviewCompression
waveCompression
waveTransverse waveTransverse wave
Ocean waveOcean wave Surface waveSurface wave
Reminders…• Energy is not created nor
destroyed; it is only converted from one form to another; i.e., chemical heat mechanical electrical
• Potential energy is energy of position; kinetic energy is energy of motion
• Forces affect motion and speed• There are different types of waves
that travel through different media»Any questions???