# Physical Science – Chapter 3 Study Guide Answers

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Physical Science – Chapter 3 Study Guide Answers

Distinguish between distance and displacement. (Know the definitions)
Distance = how far (scalar quantity) Displacement = distance and direction of an object (vector quantity)

Calculate the average speed of an object. (Know the equation)
Average speed = total distance traveled divided by total time

Explain the difference between speed and velocity.
Speed = distance an object travels per unit of time (scalar) Velocity = speed and direction of a moving object (vector)

Describe how acceleration, time and velocity are related.
Acceleration = change in velocity over time Acceleration = final velocity minus initial velocity divided by time

Explain how positive and negative acceleration affect motion.
Positive acceleration = speeding up, upward movement on the graph Negative acceleration = slowing down, downward movement on the graph

Write equations for the displacement and velocity of an object over time.
Velocity = displacement divided by time Acceleration = change velocity divided by time

Recognize and draw graphs of an objects displacement and velocity verses time.
Displacement vs. Time = VELOCITY GRAPH Time Is on X—axis, Displacement is on Y-axis, Slope = velocity Velocity vs. Time = ACCELERATION GRAPH Time is on x-axis, velocity is on y-axis, slope = Acceleration, area below line is displacement

Interpret motion diagrams
Drawings to demonstrate direction of motion, include forces if known

Explain how forces and motion are related.
In order to have motion you need an unbalanced force

Compare and contrast static friction and sliding friction.
Static friction = frictional force prevents 2 surfaces from sliding past each other

Compare and contrast static friction and sliding friction.
Sliding friction = force that acts in opposite direction to the motion of a surface sliding past another surface

Compare and contrast static friction and sliding friction.
Same = both involve surfaces, cause friction which generates heat Different = Static prevents sliding, Sliding opposite direction of motion

Describe the effects of air resistance on falling objects.
Air Resistance is a form of friction Caused by the interaction between an object and the air molecules it comes into contact with

Describe the effects of air resistance on falling objects.
The bigger the object the more air resistance The faster the object the more air resistance Without air resistance all objects fall at the same acceleration

Define motion Occurs when an object changes position

Define instantaneous speed.
Speed of an object at a given point in time

Identify situations when distance and displacement are the same and situations when they are different. Same – if you start and finish in different locations Different – if you start and finish at the same spot

Explain what happens if 2 objects have the same speed but different velocities.
Objects are travelling at the same speed but moving in different directions, or changing directions

Define acceleration. Change in velocity divided by time

When does acceleration occur?
Anytime there is a change in velocity (slow down, speed up, change directions)

What does the slope of a distance vs. time graph represent?
Speed/velocity

What does the slope of a velocity vs. time graph represent?
Acceleration

Define balanced force, unbalanced force, and net force.
Balanced force = forces equal in size but opposite in direction, cancel each other out NO CHANGE IN MOTION

Define balanced force, unbalanced force, and net force.
Unbalanced force = forces that are not equal in size and/or direction, combine to produce a net force that is not zero, can cause the motion of an object to change

Define balanced force, unbalanced force, and net force.
Net force = when 2 or more forces act on an object at the same time, sum of all the forces acting on an object