Velocity of a Car at Different Ramp Heights

Introduction

This is your introduction to mechanics! We start with a very simple concept of sending a car down a ramp.

Objectives:

  • to determine the effect of increasing ramp heights on the average velocity of a car
  • to calculate average velocity given displacement and time variables

Hypothesis:

What will happen to the average velocity of a car as it is released from increasing ramp heights? Why? (For why – hint – what force will increase as the ramp height is increased?)

Methods and Materials

Set up CPO equipment as directed.

Connect pole to triangular stand.

Connect ramp so that it is on hole #2 from the bottom.

Connect timer to power cord and to both photogates. Plug it in to power source.

Turn on timer with on/off switch. Set timer to interval mode. If CPO timer, be sure that A and B are both lit up. If gray timer, no need to do this.

Collecting Data:

  1. Attach photogate A to the ramp where it says 25 cm and photogate B where it says 52 cm.
  2. Place car at top of ramp.
  3. Press reset on your timer and let go of car making sure not to push it with any force.
  4. CPO Timer – if A and B are both properly lit up, the time it gives you is the time it took to go from point A to point B in seconds. Record this time in Table 1 below.

Gray Timer – It will automatically give only the time for the car wing to pass point B. To get the time from A to B, press and hold down the memory button. It will give you an A to B reading. Record this!

  1. Do 3 trials for this same ramp height. Record each time value in Table 1. Be sure to reset the time in between each trial.
  2. After 3 trials, switch the ramp height to 4 holes from bottom. Repeat the procedure to get 3 trials of data. And the repeat for 6, 8, 10, and 12 holes from bottom.

(Work on at least getting your average times (3 trials/3) when done with lab. Work on velocity calculations if time allows.)

Results

Table #1 – Times at Different Heights

Ramp Height / 2 holes from bottom
/ 4 holes from bottom / 6 holes from bottom / 8 holes from bottom / 10 holes from bottom / 12 holes from bottom
Trial 1 Time (s)
Trial 2 Time (s)
Trial 3 Time (s)
Average Time (s)

Table #2 – Finding Car Velocities

Ramp Height / 2 holes from bottom
/ 4 holes from bottom / 6 holes from bottom / 8 holes from bottom / 10 holes from bottom / 12 holes from bottom
Displacement (cm)
Average Time (s)
Calculated Velocity (cm/s)

Calculations (Scrap Only)

Lab Report Specifications and Hints – Velocity of a Car at Different Ramp Heights

Introduction

Background topics should include a basic introduction to the topic of mechanics – distance, displacement, speed (instantaneous vs. average), speed vs. velocity, scalars vs. vectors, acceleration, acceleration due to gravity (g), friction in general, then 4 types of friction (static, rolling, sliding, and fluid – ignore kinetic if it comes up in you research), and how air resistance relates to friction. This time your challenge is to make sure that you are actually discussing these topics and not just making a big list of definitions for them. You must explain important concepts that relate to each – NOT just quickly say what they are. Be SURE to put into own words – plagiarism is not acceptable! Check yourself on turnitin in advance of due date. Suggested length of intro is minimum 1 page of background PLUS objectives and hypotheses in another paragraph. Don’t forget to properly cite at least once per paragraph in APA format.

Include as always all objectives in past tense sentences. And also clearly include the lab hypotheses being careful to change them to past tense. (“was hypothesized x would” instead of “is hypothesized that x will” for example since lab is now done!)

Methods and Materials

Use the given procedure, noting any changes or specific additions. Be sure to put in PAST tense, passive voice sentences and paragraphs (NOT STEPS!! NOT COMMANDS!) and make the sentences read well rather than use the exact brief language used by the sheets to be concise.

Insert a picture you took of your CPO set-up when noting that the equipment was set up. You can say something like… “The CPO equipment was set us as shown in Figure 1.”

**** Very important this time – in methods you must also include these results manipulation steps:

  • How and why calculations were done, almost as if walking us through your calculations and where data came from to fit with equations. Explain that 3 trials were done and that averages were found (calcs not shown for this simple averaging). Explain velocity calcs in much more detail.
  • That line graph was created – give variables, method (numbers app, handwritten, etc.) Explain that a smooth line was drawn to connect data points.

Results

You should have 2 data tables like the one from the lab sheets recreated. Include proper units of course. Table 1 is for your raw data and Table 2 is for your summary data, post calculations.

You must also create a line graph (it will be figure 2 instead of figure 1 since image of setup is in methods) of ramp height (# of holes) vs. car velocity (cm/s). You are strongly encouraged to do this lab in the numbers app if you can figure out how to make it a line graph instead of a bar graph now. You must connect your actual data points but in a smooth line, not a rigid one so that trend can be seen. If having any trouble, you may do a handwritten graph but be sure to note in digital copy that it is appended so I can know to look for it if digitally grading again.

Calculations

There must be a subsection of calculations. Recall that the calculations subsection is underline IN methods, no bold, not its own full section.

While you need to do the calculations to get average time for each of 3 trials – you should NOT show these easy calcs. Just do them in your calculator. Keep the same decimal places as was in your trials.

There should be 6 calculations – one for the average velocity of the car at each of the ramp heights – explained below:

vavg = d

t

Be sure you are using the 3 step method EVERY time. Yes, you must rewrite the equation every single time to drive home this point and substitute in with units, etc. Bring that unknown variable down every time!! Sig figs count!! You may type the calculations (preferable) or handwrite them and note in calculations section that they are in the appendix (A or B) depending on if your graph is also in an appendix at end of report.

Discussion

Here are some hints for what you should discuss about your results….

  • Explain what was measured about the car’s journey using mechanics vocabulary.
  • Explain what happened when ramp height was increased and how gravity, acceleration due to gravity, played a role.
  • Talk about error sources VERY specifically – this time you have intro theory on friction to use as you discuss this. Friction is a common error source but you can’t just say “friction”. You should talk about all the different types of friction that came into play and when. (Hint – there were 3 different types!!) Talk about any other procedural error sources that were possibly and how they could have specifically impacted the results.
  • Don’t forget to use your results well as evidence and note specifics about them! Fig 2….
  • Explain if hypothesis was correct and why – can be done as you infer above.
  • Clearly note if and how the objectives were met. (This can be done as you discuss the results above – it does not have to be at the very end of the discussion where it might seem redundant.)
  • A good discussion this time is probably about 4 well developed paragraphs.

References

APA format as always – use my 2 page guide!!