First Semester Review

First Semester Review 2021-2022

8th grade Science

Poll

___________ occurs when force causes a change in the position of an object with respect to a referece starting point.

• Position

• Motion

• Gravity

• Force

Poll

The displacement of an object is measured using the __________.

• Distance and Direction

• Distance and Speed

• Direction and Speed

• Force and Distance

​Force and Motion

​Force: The push or pull of an object to cause it to change its motion

​Reference Starting point: Used to describe the location of an object

​Motion: Occurs when there is a change in position of an object with respect to a reference starting point.

​

​Position: The location of an object.

​Direction: The line, or path along which something is moving, pointing, or aiming.

​Displacement: The distance and direction of an object's change in position form the starting point.

Poll

When looking at a position time graph, if there is no slope the object is

• moving at a constant speed

• stopped, not moving

• turning around

• slowing down

Multiple Choice

On a graph a flatter slope means

• faster speed

• slower speed

• stopped; no motion

• turning around

Multiple Choice

On a graph a steeper slope means

• faster speed

• slower speed

• stopped; no motion

• turning around

Multiple Choice

On a graph a zero slope means

• faster speed

• slower speed

• stopped; no motion

• turning around

​Graphs

​Constant Velocity: OBject covers the same amount of distance in each time period

​Dependent Variable: Labeled on the y-axis as distance or position

​Independent Variable: Labeled on the x-axis as time

​Position-time Graph: Represents how both speed and distance/position change with time.

​Calculating Speed

• ​Instantaneous Speed: A measure of how fast something moces a particular distance over a given amount of time (ONE PORTION OF THE TRIP)

• ​Average Speed: The result of the total distance divided by the total time taken (TOTAL TRIP). Calculated v=d/t

• ​Velocity: Speed in a given direction

Poll

Julia was driving to Charleston. In the 3rd hour, she was traveling 80 mph. She was 20 mph over the speed limit. What is this an example of?

• Instantaneous Speed

• Average Speed

Poll

During Autumns trip, she travelled 215 miles in 3 and 1/2 hours. This information tells us her __________.

• Average Speed

• Instantaneous Speed

​Force of Gravity

• ​Gravity is a force that always attracts or pulls objects toward each other without direct contact or impact.

  • ​Dependent on the mass of the objects

    • ​MORE mass = STRONGER force of gravity

    • ​less mass = weaker force of gravity

  • ​Dependent on the distance

    • ​less distance = STRONGER force of gravity

    • ​greater distance = weaker force

Multiple Choice

The top image is an example of

• Strong gravitational force

• Weak gravitational force

Multiple Choice

The bottom image is an example of

• Strong gravitational force

• Weak gravitational force

​Friction

• ​A force that occurs when one object rubs against another object; opposes motion by slowing an object down o stopping it

• ​Two Factors that determine the amount of friction:

  • ​the type of surface

  • ​the mass pressing the surfaces together

Poll

If two forces are not equal and cause the motion of an object to change the speed and/or direction it is a

• balanced force

• magnitude

• unbalanced force

• friction

Multiple Choice

Balanced and Unbalanced forces have a _______ and _______. They can be represented by vectors.

• magnitude and strength

• direction and displacement

• magnitude and direction

• force and motion

​When unbalanced forces are exerted in OPPOSITE directions their NET FORCE is equal to the DIFFERENCE between the two forces.

​

​

​**Combined forces are exerted in the direction of the greater force.

​

​Balanced forces act in OPPOSITE DIRECTIONS and are of EQUAL STRENGTH.

​

​**Balanced forces cause no change in motion.

​

​If unbalanced forces are exerted in the SAME direction, the NET FORCE will be the SUM of the forces in the direction the forces are applied.

​

​

Poll

For every action, there is

• Newton's First Law of Motion

• Newton's Second Law of Motion

• Newton's Third Law of Motion

• Newton's Laws of Motion

Multiple Choice

If a book has a force of 18N pushing to the right and 20N pushing to the left, what is the net force acting on the book?

• 38N Left

• 2N left

• 2N right

• 38N left

​Waves

• ​Mechanical Waves

  • ​Require a medium

  • ​Can be transverse or longitudinal

• Electromagnetic waves

  • ​DO NOT require a medium

  • ​Can travel through a vacuum.

  • ​Transverse only

​Longitudinal Waves

​Particles of matter vibrate by pushing together and moving apart in a parallel direction.

​Transverse Waves

​Particles of matter vibrate by moving back and forth and perpendicular (at right angles)

Fill in the Blank

Which number represents the trough?

Fill in the Blank

Which number represents the wavelength?

Fill in the Blank

Which number represents the crest?

Fill in the Blank

Which number represents the amplitude?

Multiple Choice

Which choice correctly identifies A, B, and C?

• A. Wavelength

  B. Compression

  C. Rarefaction

• A. Rarefaction

  B. Wavelength

  C. Compression

• A. Compression

  B. Rarefaction

  C. Wavelength

• A. Rarefaction

  B. Compression

  C. Wavelength

​Wave Properties

• ​Speed -- Changes as it goes from one medium to another.

  • ​Electromagnetic wave travel at the same speed in an empty space

• ​Frequency -- Measure of how many waves pass a point in a certain amount of time

  • ​High frequency = many waves = more energy

  • ​Low frequency = less waves = lesser energy

• ​Wavelength -- measure of distance from crest to crest or trough to trough

• ​Amplitude -- Measure of the distance between the resting position and a crest or trough

Multiple Choice

This type of wave behavior is called

• Transmission

• Absorption

• Translucent

• Reflection

Multiple Choice

This type of wave behavior is called

• Transmmission

• Reflection

• Refraction

• Scatter

Multiple Choice

This type of wave behavior is called

• Reflection

• Transmission

• Absorption

• Refraction

Multiple Choice

This type of wave behavior is called

• Reflection

• Transmission

• Absorption

• Refraction

​Light Waves

​Amplitude

• Higher amplitude =  brighter light

• Lower amplitude = dimmer light

Speed

• Light waves travel at the same speed in an empty space (vacuum). 

Speed changes as they travel from one medium to another. 

​Light Wave Behaviors

​Refraction

​- Light waves through a convex lens will make images appear larger as the light waves bend

​- Prisms separate while light into different colors.

​-Light is bent at different angles depending on the frequency

​ - Red = lowest frequency

​ - Violet = highest frequency

​Transmission

​- Transparent & translucent materials transmit light

​ - Transparent: allows most light through

​ - Translucent: transmit some light (NO clear image)

​-Opaque objects allow NO llight wave to pass through (Cannot See Through)

​Reflection

​- Plane mirror reflect light to form clear images

​- Colors reflected can be seen by the human eye

​- Objects that reflect all light appear white

Absorption

​- Some opaque objects absorb light waves

​- Heat energy is generated when absorption occurs

​- Colors that are absorbed are NOT seen

​- Objects that absorb all light appear black

Multiple Choice

Regulates the amount of light entering the eye and gives the eye its color.

• Iris

• Lens

• Pupil

• Retina

Multiple Choice

The clear tissue that covers the front of the eye.

• Lens
• Pupil
• Iris
• Cornea

Multiple Choice

What is letter B

• Optic nerve
• Lens
• Cornea
• Retina

Multiple Choice

What is letter C

• Vitreous humor
• Lens
• Optic nerve
• Cornea

Multiple Choice

What is letter E?

• Vitreous humor
• Retina
• Cornea
• Optic nerve

Multiple Choice

What is letter F?

• Retina
• Pupil
• Vitreous humor
• Iris

Multiple Choice

What is letter G?

• Sclera
• Retina
• Lens
• Vitreous humor

Multiple Choice

What is letter H?

• Cornea
• Optic nerve
• Iris
• Retina

Multiple Choice

What is letter I?

• Cornea
• Lens
• Vitreous humor
• Optic nerve

Multiple Choice

Pupil

• Focuses light
• Clear tissue that covers the front of the eye
• Opening through which light enters the eye
• Layer of receptor cells

Poll

Do you feel like you will do much better on your SLO tomorrow?

• Yes

• No

• I still have some questions

• I didn't even try the first time