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