GALILEO 2 LAB

NAME _________________________ PERIOD _____ DATE __________

PRE-LAB: DIFFERENT KINDS OF SPEED A. Even though it doesn’t make much sense to calculate the slope of a curved graph, you can still do it. To calculate a slope, you divide rise by run. So let’s do that for your graph from Part 2 (marble down the ramp) of your lab from last time. Pick your last data point and enter those numbers in the appropriate boxes below. Rise 

Total distance traveled  =

Run 

Total time elapsed 

B. Was the speed of the ball when it first began rolling greater than, less than, or equal to the number you calculated in step A?

C. Was the speed of the ball when it was rolling at the bottom of the ramp greater than, less than, or equal to the number you calculated in step A?

The number you calculated in step A is called the average speed. In this lab, you will use a tool called a photogate to measure the speed of the marble at any one particular time. This speed will be called instantaneous speed.

MARBLE ON THE RAMP AGAIN You will again consider the motion of the marble while it is on the inclined ramp. This time, though, you will use photogates to measure the “instantaneous” speed of the ball at various times. A. Predict what a graph of (instantaneous speed of the marble) vs (amount of time traveled) for this marble would look like. Sketch the graph on the right. B. Set up the photogates at the bottom of the ramp, as shown in class. You’ll release the marble from different positions along the ramp. For each release position, record (1) the time it takes the marble to reach the photogate (using the stopwatch); and (2) the speed of the marble registered by the photogate (on the computer screen, use the units given by the computer).

BEFORE YOU BEGIN, RE-READ STEP B ABOVE!!!!!

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C. Use your recorded data to draw a graph of speed vs time for the marble rolling down the ramp. Analyze this graph as you did in the last lab, as appropriate. DRAW A BEST FIT LINE. Data:

Graph:

Slope (remember to use points off the best fit line!):

What does the slope mean? (think about the units)

Write an equation of this line (y = mx + b), then substitute the variables for y and x for your data. Be sure to include the units for the slope. (Hint: look back at your day one notes) y

=

m

x

+

b

Physical variable Variable units Final Equation:

D. Is the speed of the marble constant as it rolls down the ramp? What about the speed-time graph tells you this?

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G. What would your speed-time graph look like if you increased the angle of the ramp?

H. Would the slope value change? If so, how?

Teacher Check In ___________________ I. Repeat the steps for a steeper ramp. Data:

Graph:

Slope (remember to use points off the best fit line!):

What does the slope mean? (think about the units)

Write an equation of this line (y = mx + b), then substitute the variables for y and x for your data. Be sure to include the units for the slope. (Hint: look back at your day one notes) y = m x + b Physical variable Variable units Final Equation:

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POST-LAB: FOLLOW-UP A. What does the distance-time graph of an object with constant speed look like?

B. What does the distance-time graph of an object with increasing speed look like?

C. Can an object have increasing speed and still have some kind of uniformity about its motion? Explain.

D. What does the speed-time graph of an object with constant acceleration look like?

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E. Matching: There are three columns - increasing speed, constant speed, and decreasing speed. Underneath each column, list the item number from each group that belongs in that column. Increasing Speed

Constant Speed

Decreasing Speed

1. zero acceleration 2. negative acceleration 3. positive acceleration

4.

7.

5.

8.

6.

9.

10. 11. 12.

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