Acceleration, Velocity, Speed

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

•  $\Delta$  is a symbol that means a change in something...so when you see that symbol of the triangle you know you will be subtracting the initial velocity from the final velocity

• a is the letter that means acceleration

• t is the letter that means time

Multiple Choice

 $\Delta v=45\ \frac{m}{s}$  

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

•  $9\ \frac{m}{s^2}$  

•  $5\ \frac{m}{s^2}$