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???