Speed, Velocity, and Acceleration

Acceleration, Velocity, Speed

Lesson #2 taking velocity and speed and adding acceleration to our understanding.... PHYSICS IS GETTING PHUN!!!

Multiple Choice

Speed is a measure of

• distance covered in an amount of time

• distance divided by time

• both of the other choices are correct

• none of the choices are correct....speed is a vector

Multiple Choice

The velocity of a car heading 100 miles west in a time of two hours will be

• 50 miles/ hour West

• 50 miles/ hour

• 0.5 miles/ hour

• 0.5 meters/ second West

ACCELERATION

Acceleration is a vector quantity that is defined as the rate at which an object changes its velocity. An object is accelerating if it is changing its velocity.

EXAMPLES OF ACCELERATION

Acceleration could mean speeding up....that is the obvious one of course.

EXAMPLES OF ACCELERATION CONTINUED

Acceleration can also mean to SLOW DOWN! Yes....acceleration actually means any change in speed even if that means slowing down.

HERE IS THE WEIRDEST THING ABOUT ACCELERATION....

Acceleration not only means a change in speed (either speed up or slow down) it also means a change in DIRECTION.....Yes, when you go around a curve or turn one way or another even if you do it slowly you are considered accelerating!!!

Multiple Choice

A car is safely speeding up from 10 miles per hour to 50 miles per hour. what is the car doing?

• accelerating

• speeding

• stopping

Multiple Choice

A car is slowing down from 50 miles per hour to 20 miles per hour...what is the car doing?

• accelerating

• accelerating

• accelerating

• Yes....the correct answer is accelerating! Pick this one!

Multiple Choice

A car comes to a curve in the road and proceeds to safely follow the curve and keep on going...what did the car do in the curve even though it never changed its speed?

• the car accelerated by simply changing direction and keeping its speed the same

• the car simply turned...it has nothing to do with acceleration

Multiple Choice

According to the video you just watched, What is the units for acceleration?

• M / s²

• Meters per second squared

• meters per second per second

• all of these are correct

Multiple Choice

If a car goes from zero to 50 meters/ second in 30 seconds, what is its acceleration?

• 1.7 meters / second squared

• 0.6 meters / second squared

Multiple Choice

If a car goes from 10 meters a second to 50 meters a second in 6 seconds, what is its acceleration? (remember to subtract the final speed from the initial speed to get your actual speed)

• 6.7 meters per second squared

• 0.15 meters per second squared

• 6.7 miles per hour

• 0.15 miles per hour

Multiple Choice

What does initial velocity and mean?

• Initial velocity is the starting value of an objects velocity before something happens to change it

• Initial velocity is the speed when something changes

• initial means the letters of my name

• initial is the last velocity something has

Multiple Choice

A bicycle and rider are rolling along at a velocity of 15 meters per second and crash into a brick wall reducing their velocity to zero meters per second in 0.5 seconds. What was their negative acceleration in this instance?

$$0\ \frac{m}{s\ }\ -\ 15\ \frac{m}{s}\ \div0.5\ s\ =$$  

• -30 meters / second squared

• 30 meters/ second squared

• 15 meters/ second squared

• -15 meters/ second squared

Multiple Choice

If an object is speeding up what is the value of the acceleration?

• positive acceleration means speeding up

• positive acceleration means slowing down

Multiple Choice

If an object is slowing down what is the value of acceleration?

• slowing down will give us a negative acceleration value

• slowing down will give us a positive acceleration value

examples of acceleration review

• speeding up is considered a positive acceleration

• slowing down is considered a negative acceleration

• changing direction could be either a negative or positive acceleration depending on the change that takes place

Calculating acceleration

Multiple Choice

$$\Delta v=45\ \frac{m}{s}$$  

$$t=5s$$  
What is the acceleration of this system?

• $$9\ \frac{m}{s^2}$$  

• $$5\ \frac{m}{s^2}$$  

Motion Graphs

​At the end of lesson, you should be able to interpret and analyze data about speed, distance, velocity, acceleration and time from graphs.

by Ms. Taylor

​

​Use to aid with the completion of the Graphs Foldable

**​ALWAYS pay attention to the labels on Axes!!

​Motion graphs-

​This is a graphical display of the relationship between speed, velocity, distance and time and acceleration. Just as a reminder, the definitions of common terms are below:

​Acceleration - the rate of change of velocity per unit of time. (Vector quantity)

Displacement - the amount by which a thing is moved from its original position. (Vector quantity)

Distance -  an amount of space between two things or people. (Scalar quantity)

Mass - the amount of matter in an object. (Scalar quantity)

Speed - distance an object travels per unit of time. (Scalar quantity)

Velocity - speed and direction of a moving object. (Vector quantity)

​PART A

Multiple Choice

On a distance vs. time graph, the steeper the slope _____

• the slower the speed
• the faster the speed
• less acceleration
• greater acceleration

Multiple Choice

On this position vs time graph, describe the motion of A.

• constant positive velocity

• constant negative velocity

• positive acceleration

• negative acceleration

• velocity is zero

Multiple Choice

 The graph shows Ashley riding her bike to Maria's house. 
What is occurring from point A to point B?

• they are traveling at a constant speed
• they are decreasing in speed
• they stopped to take a break

Multiple Choice

What is happening at B?

• Stationary
• Accelerating
• Steady speed; moving away from the starting position

• Steady speed; returning to start position

Multiple Choice

What is this graph showing?

• Constant Speed
• Acceleration (speeding up)
• Deceleration (slowing down)
• No motion

Multiple Choice

What does this graph represent?

• Constant speed
• Acceleration
• Not moving

Multiple Choice

Susie went to the store, when she got there she realized that she forgot her wallet and returned home.

Which graph matches this motion?

Multiple Choice

Which runner stopped for a rest?

• Albert
• Bob
• Charlie

Multiple Choice

Which graph shows the object standing still?

• A
• B
• C
• D

​Calculating from graph

​ You can calculate the average speed/velocity from a distance time graph. To do this:

​1. determine the total distance

​2. divide by the total time it takes to reach final

distant (final time -starting time)

​

​ex. Calculate the speed of the object in graph.

speed= distance/time

​speed =200/4

​hence, speed = 50 m/s

Multiple Choice

On this position vs time graph, what is the velocity?

• 40 m/s

• 8 m/s

• 5 m/s

• 0 m/s

Multiple Choice

Which runner won the race?

• A
• B
• C

Multiple Choice

Anne cycles from Bristol to Salisbury.

The diagram shows the distance-time graph of her journey.

What is Anne's speed for the first two hours of her journey?

• 40 mph

• 30 mph

• 20 mph

• 10 mph

​PART B

• ​Steeper the diagonal means faster acceleration.

• ​Deceleration means negative acceleration-diagonal line going down

​Summary

Multiple Choice

What is this graph showing?

• At rest

• Acceleration

• Constant speed of 1 m/s

• Gradually speeding up

Multiple Choice

What is this graph showing?

• Fast constant speed

• Slow constant speed

• At rest

• Accelerating

Multiple Choice

What is this graph showing?

• Constantly slowing down

• Constantly speeding up

• Acceleration

• Returning to starting point

Multiple Choice

• Accelerating gradually

• Stopping

• Slowing down constantly

• Speeding up constantly

Multiple Choice

At what point is the speed the greatest?

• C-D

• B-C

• A-B

• D-E

Multiple Choice

Match the graph to the description:

"The car is accelerating at a constant rate."

Multiple Choice

What does this graph represent?

• Constant speed
• Acceleration
• Not moving

Multiple Choice

In which of the following graphs below are both runners moving at the same speed?