Investigating the speed of a spherical object on a slope.

Prediction

I think that when I change the height of the slope (my variable) it will effect the speed of the spherical object.  I predict that when the height of the slope is increased (the slope becomes steeper) the marble will travel faster.  I believe the marble will travel faster (over the same distance) down a slope, which is tilted at one end at the height of 70cm from a surface than a slope, which is tilted at 20cm from a surface.

The reason I think this will happen is because of the behavior of gravitational potential energy (GPE) and kinetic energy (KE).  

When the marble is held at the top (or a point) of the slope it has GPE and when it is let go the GPE is transferred into KE.  The theory is that the KE gained is equal to the GPE lost.  Therefore when there is more GPE to be lost there will be more KE to be gained and the energy is what the marble or spherical object needs to move so more energy equals greater speed.

The reason that my chosen variable, the height of the slope, will increase change the speed of the marble is because height increases GPE.  When there is a greater height there is more gravity, which makes more GPE.  As you can see in the formula for GPE

GPE equals mass times g (gravitational field strength = 10m/s squared) times height.  So this evidence leads me to believe when there is a steeper slope, there is a greater height, which will equal a greater GPE.  Which then equals a bigger energy transfer from GPE to KE so the marble will have more KE as it travels down the slope which will increase its speed.

Procedure

Apparatus

Here is a list of equipment I will use during my experiment:

• Metal (steel) triangular hollow ramp at least 1 metre long

• A regular sized marble with a diameter of about 1.9cm

• Stop clock or stop watch    
• Metre rule
• Marker pen
• Clamp stand

Method

1. Collect the apparatus shown listed above and set them up like the diagram.  Rest the slope on the clamp stand at any height to start with.
2. Adjust the clamp stand so the slope rests on a point, which is 20cm from the surface you are working on.
3. Measure 1m from the end of the slope (the end which is resting on the working surface) with the metre rule and mark the point with the marker pen.
4. Hold the marble on the slope where the marked point is and get the stop clock or stop watch ready.  Remember to reset the clock so it is at 0:00oo.
5. Then release the marble, pressing the stop/start (once) at the same time.  Watch the marble closely as it travels down the slope and press the stop/start button (once) again the instance the marble reaches the end of the slope and hits the surface you are working on.  Record the time on the ‘results table’.
6. Repeat the process with the 20cm as many times as the ‘results table’ shows.  Remember to record each time and reset the stop clock or stop watch before each try.
7. After recording all the results needed for 20cm adjust the clamp stand so the height reaches 30cm and repeat the process to record results.  Then repeat it again at the height of 40cm then 50cm, 60cm, and 7cm.  Put all results in the ‘results table’ (in ‘results’ section).

Diagram

Fair Test

To keep the practical a fair test:

I will try not to change anything but my chosen variable and will keep measurements and recordings accurate.  When adjusting the height of the slope to make it steeper or less steeper I will make sure that I have accurate measurement of height (e.g. 70cm=70cm) and that I do not move the slope so the 1m reading is inaccurate. To do this I will always check (two or more times) that height is accurate to the measurement needed and will also check (two or more times) that the 1m mark equals 1m.  If the readings are not accurate I will adjust the stand or slope so it is right again.

I will also assure that I reset the clock before every try so the results are correct.  I will try to handle the marble and slope as little as possible so the variable temperature is not varied.  Other obvious things I will do are included in the ‘variable section’.

 

 Results

*Time for marble traveling over 1m with the slope resting on clamp stand at height of …cm from work surface.

Safety

To make the investigation safe I will do things such as:

• Make sure I am not in the way of anyone else in the working area so that fast moving or heavy apparatus (e.g. marble traveling fast, heavy clamp stand falling) don’t hurt him or her or me.
• Catch or stop the marble, in some way, from rolling out of my working area as it comes of the slope. This will prevent the marble interfering with other pupils so no one is hurt.
• Not walk through other peoples experiments incase I disrupt there experiment hurt them or hurt myself.
• Make sure the clamp stand is in no way going to fall or let the slope drop by checking if it is secure on every test.  This will prevent the clamp stand or ramp damaging any pupils.
• Make sure the slope is resting on a secure work surface that can take the weight and will not let the slope slip.  This will prevent injury from the slope hitting any pupils.
• Make sure I do not leave bags, books or apparatus that is not in use around my work area or anyone else’s so that it does not disrupt experiments or cause injuries.  I will keep equipment in a safe place (e.g. under the table).

 

Preliminary Work Summary

My ‘preliminary work’ helped me to decide how to plan this experiment by providing me with a good look over what variables I could work with. It gave me the chance to test out all of the variables and figure out which one I would be best suited working with.  Some of the variables I tested would have been very hard to use and it would be hard to come up with accurate results and a sensible evaluation.  If I varied friction for example it would have been hard to use different amounts of friction as I would have to research properties of materials and it would be hard to keep measurements consistant.  Also I found that some variables had little effect and would have little point investigating.  Colour as a variable would not effect the speed at all so I would find it hard to draw a valid conclusion.

Also the ‘preliminary work’ provided me with valid insights and understandings of what measurements would need to be taken and how they would be taken.  In the ‘preliminary work’ I found that I would use a maximum slope height of 70cm and a minimum of 20cm.  This gave me a decent range, which would enable me to get enough results to draw a good conclusion.  I found that if I went below 20cm the speed of the marble would be very low and would take a long time to record results.  I found that if I went above 70cm the marble would be hard to see as it traveled so it would be hard to know when to start and stop the stop clock.  So then I may get inaccurate results.

The other things I found in my ‘preliminary work’ were that:

• The triangular hollow metal slope made it easier to record the marble as it traveled down the slope, as the flow was regular.  It also insured that the marble did not drift of the ramp like it might have done on a wooded one with no guards.
• The regular marble gave a spherical object size that was easiest to use.  This was because the object: would fit on the slope with no chance of it falling of, gave a mass that would not move extremely quick and was easy to see so times could be recorded accurately.

Results

Try 1

Try 2

Average table:

Conclusion

From my graph I can see that my pulse rate rises rapidly throughout the exercise and then slowly decreases after it, it then continues steadily at the same rate as it was before the exercise, when I was using little energy.

The shape of the line of ‘best fit’ shows a rapid rise in each of the variables until the exercise is over when each of the six variables steadily fall. The pattern of the results shows that if I had carried on taking my pulse each minute after the exercise, the line of ‘best fit’ would become a straight line continuing steadily onwards.  I changed my variable six times to get a wider range of results and enable me to draw the best possible conclusion. The wide range of my results helped me to draw a more accurate conclusion because I was able to represent them in the form of a graph and see easily what was happening.

I conclude that when the time of exercise is increased the heart rate is higher and when the time of exercise is decreased the heart rate is lower. This is because the rates at which my muscles contract and relax during exercise increases, resulting in a lack of oxygen and muscle nutrients. This lack of oxygen causes an increase in the caliber of blood vessels allowing the blood to flow back to my heart more easily, which in turn increases the load on my heart and causes my heart muscle to strengthen and beat faster.  The deep breathing I felt at the end of the exercise was caused by an increased circulation in the capillaries surrounding my alveoli.  

For a short while during exercise glucose may be used without the benefit of oxygen, this is called anaerobic respiration (as opposed to aerobic respiration which uses oxygen), this allows a greater amount of activity than would otherwise be possible, e.g. sprinting instead of jogging. This causes a greater strain on the heart, which in turn causes the heart muscle to be strengthened and pump faster, the longer the exercise the faster the heart pumps to remove lactic acid which is created during anaerobic respiration i.e. the heart rate is increased. This shows my original prediction turned out to be correct.

Evaluation

 

I think my procedure worked well and enabled me to obtain a reasonable set of results.  The way I made my experiment a fair test is by placing a chair close to where I did the exercise. By changing my variable a number of times I got a wider range of results which enabled me to draw a more accurate conclusion.  I did the whole experiment twice in order to be able to:

1. Calculate an average of the two tables
2. Have enough information to make a graph
3. Exclude any wild differences in the two sets of results i.e. I may have accidentally taken my pulse wrongly in the first set of results, however, when calculating the average this result was evened out, avoiding an anomalous readings.

I think my graph was good enough to support my conclusion, it shows a clear line of ‘best fit’ that backs up the fact that the longer we exercise the greater the increase in the heart rate.  It also shows a steep rise in the line of ‘best fit’ until the point where the exercise stopped and the line descends steadily.  From my scientific knowledge and understanding I know that if I had continued to take my pulse rate for every minute after the exercise, the line of ‘best fit’ would show a relatively straight line until I actual started to use energy again in which case the line would rise.

Other methods I could have used to give me extra measurements to support my conclusion could have been to do the whole procedure three times instead of two, this would give me a wider range of results and a better average.

I think my measurements fit relatively well on to my graph although I have been left with a few anomalous points, I feel this has happened because of inaccurately reading my pulse wrongly at points. To improve my results and avoid anomalous points I could have used a heart rate monitor to take my pulse, this would be much better and more reliable than taking it myself as I did. Alternatively having someone else to record my pulse leaving me to concentrate on the exercise, it was difficult to both perform the exercise, and then be responsible for recording the results and made it easier to make a mistake.  Most of my anomalous points occur further towards the point where I stopped exercising, this may be because my heart rate was highest at these points so I may have miscounted because the beats were too fast. My results look relatively similar to each other apart from some results which occurred later in the experiment. These results are probably due to inaccurate recording of my pulse.  Other than this my graphs are very similar to each other.

My results support my conclusion reasonably well.  The graph helps to support my conclusion because most of the points fit to the line of ‘best fit’ and the line itself clearly shows what I am trying to get demonstrate in my conclusion. The line of ‘best fit’ should have taken one of two shapes, either rise in a straight line then fall in a straight line at a lower gradient or do the same but fall at a curve slowly straightening itself out. An important point to remember is that my results are unique to fitness or after people of similar fitness.  If someone fitter/unfitter than me did this experiment the graph would look relatively the same, however their pulse rates results would be lower if they were a fit person or higher if unfit.  Therefore my conclusion works for everyone.