- I collected the following equipment: ruler, ball, ramp, books, and stop clock
(I collected the bigger ramp because I know that with a bigger one I would have fewer errors).
- I then weighed the mass of the 3 balls, which I chose to use.
- Next I placed the ramp on the books, and measured its vertical height.
- I marked my starting and finishing points and them measured the distance of how much the balls were going to roll.
- I rolled the 3 different balls 3 times each and recorded the time it took them.
I experimented with 3 different balls, as I wanted to see which one I felt more comfortable using. I decided to use the ping-pong ball for my actual experiment.
The aim of this investigation is to investigate how steepness affects speed so I will use the following formula to work out the speed of each ball from the average result.
From the above set of results I can see that as I increased the height it took less time for the ball(s) to roll down the ramp. Because as the ramp gets steeper there will be less force balancing the weight, thus, there will be a greater resultant force. However I only tried two different heights so the results are not very reliable.
After carrying out my preliminary work I realised that I could have made the test more reliable. For my actual experiment I will use six different heights and repeat each experiment five times to get more accurate results. Also I will calculate the angle of the ramp at each stage to ensure my results are correct.
I think it is important to space my heights out in a suitable range so it enables me to observe clearly how the steepness affects the speed. I am going to use the following heights: 4cm, 7cm, 15cm, 18cm, 23cm, and 30cm.
After carrying out my Preliminary run I realised that I could have made the test more accurate to get more reliable results. In my experiment I will take in to consideration the following;
- I will make sure that I roll my ball the same distance in all the different heights.
- I will try to push the ball with the same force each time
- I will use the same books to hold my ramp up each time to ensure that less errors are made
- I will calculate the angle of the ramp so I can check that as the height increases so does the angle. I will use the following formula:
Horizontal -inverse tangent
I will calculate this angle
Safety is very important in a scientific experiment even if the experiment may seem harmless. To make this experiment safe I will make sure equipment is always handled with a lot of care to avoid an accident. Also I will not run around as one could get hurt. Also I will keep the desktop that I am working as clean as possible, so that there is nothing on the desktop, except for the apparatus needed thus; an accident does not happen. If an accident does occur I will inform the teacher straightaway.
- Stop clock
- Mass scale
1. Get a ball and weight it
2. Collect your ramp, books, ruler and stop clock
3. Decide the vertical
height and place the
suitable number of books
for that height
4. Decide the distance the
ball is going to roll down
the ramp and mark your
starting and finishing point
5. Start your clock
immediately after you let
the ball loose
6. Stop the clock
immediately after the
ball has passed the
finishing line and record
7. Repeat the test at least 2 more times to get reliable results
8. Do same for all the different steepness
I found out that as I increased the height of the ramp it took less time for the ball to roll down the ram i.e. the speed of the ball increased. From these set of results it shows that my prediction was correct.
From my results indicated in the graph I can see that they agreed with my prediction. I predicted that as the steepness of a slope increases the speed of the ball also increases. This is because there is less reaction force balancing the weight as the slop gets steeper, thus there is greater resultant force.
I expected that the graphs would look as follows:
A curved line showed the steepness against the speed. This shows a clear pattern, because it confirms that as the steepness increases so does the speed. When the ball sets off first, it has much more force accelerating it than the resistance slowing it down. As the speed increase the resistance builds up. This slowly reduces the acceleration until finally the resistance force will be equal to the accelerating force and then it won’t be able to accelerate any more. It will have reached maximum speed or terminal velocity
The pattern shown in the graph shows my prediction was correct. This is because it follows the 2nd law of Newton- A resultant force means acceleration. If there is an unbalanced force, then the object will accelerate in that direction.
The curved line produced on my graph is valid, as there is an obvious link between the speed and the height. Also my graph agrees with my hypothesis as it shows that at a higher steepness the ball rolls down quicker. Because as the ramp gets steeper there is less reaction force balancing the weight so there is greater resultant force Although I have two anomalous results they are not very far from my line.
In my graph I have one anomalous result (labelled on the graph). This could be due to my timing being incorrect. However it is quite close to my curve so it shows that my graph pattern is valid
After studying my graph I know that it is good enough to support a valid conclusion because as I increased the height it took less time for the ball to roll down the ramp. Also because my anomaly is very close to my curve and follows the overall trend it shows that my results are reliable.
In general the method used was suitable for the experiment, however I think that to obtain more reliable and valid results, improvements could be made.
- From the curve I produced on graph one; I can see a clear distance between some points. To plot a better curve it would be better to take more results in between the range.
- Instead of using books to support the ramp I could use some device that could be changed in height and had measurements on them, so this would give more accurate height measurements.
A "starting gate" could be used to avoid any movement before. The starting gate could be a pencil or small ruler which holds ball in place, to be let go when timing starts. This is to ensure that the initial speed is zero, i.e. Stationary.
To stop the timing I could have used a flat object such as a ruler or the cover of a book as a physical stop. This would allow me to you to use my sense of hearing along with sight to stop the clock when it hit the object.
Another way to record the time would be to use a light gate. This would be connected to a computer light and it would indicate when the ball passes the points at the top and bottom connected to the lights.
gate Finishing light
On the whole I think my experiment went really well. I believe that I carried out my experiment reasonably, and I encountered no problems. As a result I ended up with an applicable set of results.
I could carry out another experiment that would be quite similar to this one. I could investigate how the mass of a ball affected the speed. The two changing variables would be the weight of the ball and the steepness of the slope. Fair testing and safety would be just as important. I would have to use the same apparatus and overall the same method. Also all the improvements I mentioned above I could use for this experiment.
I would predict that the ball with greater mass would roll down the slowest and the ball with the least mass would roll down the fastest. This is because a greater force would be needed to accelerate the ball with more mass, whereas a smaller amount of force would be needed to accelerate the ball will less mass. Also my preliminary run backs up my prediction as I can see that it took the three balls at the same height different speeds to roll down.