They Might be Giants-Speed and Velocity

1. 
   What is the difference between speed and velocity?
   
2. 
   Give an example of speed.
   
3. 
   Give an example of velocity.
   

Example:

• 
  If I row a canoe at a speed of 2 mi/hr against a current that is going 1 mi/hr, then my velocity is 1 mi/hr upstream.
  
• 
  If I turn around and row the canoe with a speed of 2 mi/hr with the current that is going 1 mi/hr, then my velocity is 3 mi/hr downstream.
  

1. Johnny is standing up on the school bus tossing a ball up and down in front of him.

a. Ginny is sitting on the bus watching the ball. What does she see?

b. Sarah is standing on the side of the road watching the ball as the school bus drives by.

What does she see?

c. Ginny’s frame of reference is _____________________ Sarah’s frame of reference is ___________________.

2. Do the following describe speed or velocity?

a. A car traveling at 75 mi/hr

b. An object falling downward at 15 m/s

c. A bird flying at 5 m/s southwest

d. A worm crawling at 0.5 cm/s

3. Give an example of an object that is changing velocity, but not changing its speed.

4. Jane walks at a rate of 3 m/s. While at the airport, she gets onto a travelator (“moving sidewalk”) traveling 2 m/s.

a. If she stands still while on the travelator, what will her velocity be?

b. If she walks while on the travelator, what will her velocity be?

c. Jane realized that she forgot her ticket and turns around on the travelator and walks the opposite direction. What is her velocity now?

Speed (Velocity) = plus direction

Note: this is the formula for average speed or constant speed, not instantaneous speed.

1. Solve for distance:

2. Solve for time:

Steps to solve problems:

1. Circle what you are asked to find (you may need to “translate”)

• 
  How far = distance
  
• 
  How fast = speed
  
• 
  How long = time
  

3. Check that your units “match”.

4. Write down your formula and rearrange for what you’re asked to find.

5. Put in numbers for symbols and solve.

1. 
   Luke is getting his pilot’s license. He flies from Houston to San Antonio, a distance of 185 miles. If he makes the flight in 1.75 hours, what is his average speed for the trip?
   

2. 
   Beatrice runs 3 miles (1 mile = 1600 meters) every morning before school to train for the upcoming track season. If she can run 3 meters per second, how long does it take her to complete her morning workout (in seconds)?
   

3. 
   A school bus travels 15 kilometers in 0.75 hours. What is the speed of the school bus?
   
4. 
   An object travels at a speed of 50 km/hr for 24 hours. What distance does it cover?
   
5. 
   A cyclist travels 10,000 meters at a speed of 2.5 m/sec. How long will it take to complete the trip?
   

1. 
   What is kinematics?
   
2. 
   What is velocity?
   
3. 
   How is speed measured in the NFL?
   
4. 
   What does acceleration describe?
   
5. 
   What is the difference between acceleration and velocity?
   

There’s been an assassination at the new Glendale football stadium. Somebody in the rafters shot a player standing on the sidelines. The suspect managed to escape from the stadium before authorities could grab her/him.

The crime lab has done the math and it turns out that in order for this shot to be pulled off from the rafters the bullet had to have an average speed of at least 500 m/s in order for it to break through the player’s helmet. Also, in order for the bullet to reach that speed in time, it had to have an average acceleration of at least 350 m/s².

You rounded up 4 suspects: Manny, Moe, Jack, and Larry. Each suspect has a different type of rifle. You take each rifle to the shooting range and use special cameras to measure the distance the bullet has travelled over time. These observations are recorded below.

1. 
   Use the observations in the table above to complete the distance vs. time graph set up for you below. The line for Larry’s gun has already been completed. You must create the lines for Manny, Moe and Jack. Be sure to label your axes (including units) and give the graph a title.
   

2. 
   Use the slopes of each graph to calculate the average speed for each gun. Remember: Average speed = total distance/total time. Show your calculations below and INCLUDE UNITS!!:
   

Moe =

Larry =

3. 
   From your results in #2, who are the possible gunmen? Explain why.
   

Above is a graph of bullet speeds vs. time for Manny and Larry’s guns. Use this graph to answer the following questions.

4. 
   For each gun, describe whether the bullets are speeding up, slowing down, or moving at a constant speed. Also describe whether the rate of acceleration is increasing, decreasing, or staying constant.
   

Larry’s gun =

5. 
   Calculate the average acceleration of the bullets from each gun. Include units! Remember: Ave. acceleration = (Final speed – Initial speed) / Time
   

Larry =

6. 
   From these calculations, who must be the murderer? Explain why.
   

Acceleration is a vector, so it has a direction associated with it. The direction of the acceleration vector depends on whether the object is speeding up or slowing down.