Hypothesis

I predict that as the amount of force applied to the trolley increases, the acceleration will increase in direct proportion. I believe this will happen because according to Newton’s Second Law, increasing the force increases the acceleration, provided the mass stays the same. Therefore, acceleration is directly proportional to the force applied.

Fair Test

Without fair testing the experiment would be useless because the information gathered would not be accurate or reliable. Here are the things we did to ensure our experiment was a fair test:

* The distance travelled; the mass and weight of the trolley shall remain constant, as these are not the factors we will be changing.

* The only thing we will change will be the force applied to the trolley. No force will be applied to the trolley when it is at the top of the runway, instead we will just let go of it and let gravity be the force.

* When putting the trolley at the top of the runway we will make sure that the back wheels of the trolley are touching the ticker timer – this way each experiment will start in the same place.

* We will test the trolley beforehand to ensure all wheels were working, because if one or more wheels are not working this could affect the speed/acceleration of the trolley.

Safety Precautions

As with all experiment, safety is crucial. Every experiment possesses some form of danger and through these guidelines I hope the risk of danger will be minimised:

* Make sure the trolley is stopped before it reaches the end of the runway where the pulley is to prevent damage to trolley, runway or pulley.

* Make sure that when catching the trolley at the opposite end of the runway you are not in front of it before it reaches a halt as it could cause an injury

Ticker Timer

For this experiment we shall use a ticker-timer to record our results. A ticker-timer is a way of analysing the motion of objects. As the trolley moves, it drags the tape through the ticker timer, thus leaving a trail of dots, which were printed there by a vibrating metal bar running on an electric current, which hits a piece of paper fifty times a second. The analysis of a ticker tape will reveal if the object is moving with constant velocity or accelerating. This is how we hope to record the acceleration of our trolley. To get the results from the ticker timer tape, you need to divide the tape into five dot strips, this is because each five dots is equal to 0.1 seconds.

Preliminary Work

Before the actual experiment took place, we decided to do some preliminary work. There was a chance that something could go wrong, for example, the trolley could hit the side of the runway, or the weights could fall off or the ticker timer would not be entirely accurate. So we gave the experiment a test run to make sure everything worked according to plan. The test run went smoothly and so we all agreed the experiment would be a success

Prediction Graph

Equipment

* Runway

* Trolley

* Metre Stick

* Ticker Timer

* Roll of ticker timer tape

* Pulley

* String

* Weights

Diagram

Method

First of all we collected all of the equipment. Then we placed the runway on a raised surface approx. a metre above the floor. Once this had been done, we prepared the ticker timer at the top of the runway. We did this by cutting ticker timer tape to 85 cm (We chose this length because the tape will be out of the ticker timer before the weights hit the floor).

Next, we plugged the wires into the ticker timer in their rightful places and threaded the ticker-timer tape through the ticker timer. Then we placed the trolley at the top of the runway. We then stuck the ticker timer tape to the back of the trolley with tape. Next, we threaded a piece of string through the trolley and attached it to the pulley at the opposite end of the runway. To the end of this string we added different weights according to which experiment we were on. We started with 100g that is equal to 1 Newton in force. Then, on the count of three we simultaneously turned on switched on the mains, which activated the ticker timer and let go of the trolley, which caused it to roll down the runway. It rolled down the runway because the force of gravity acting on the weights pulled it. Once the ticker timer tape was out of the ticker timer we stopped the trolley to prevent it from hitting the pulley at the bottom end. We then switched off the ticker – timer. We then labelled the piece of ticker timer tape to refer to when writing down our results. We then repeated this process for 200g, 300g, 400g, 500g, 600g, 700g, 800g, 900g and 1000g.

Results

Force = 1N

Acceleration = (final speed – start speed) ? time taken

Final speed = length of last five-dot strip ? time taken

Time Taken = number of five dot strips x 0.1 seconds

Final speed = 11.8 ? 0.1

=118 cm/s

Time Taken = 12 x 0.1 seconds

= 1.2 seconds

Acceleration = (118 cm/s – 0 cm/s) ? 1.2 seconds

= 98.3 cm/s

Force = 2N

Acceleration = (final speed – start speed) ? time taken

Final speed = length of last five-dot strip ? time taken

Time Taken = number of five dot strips x 0.1 seconds

Final speed = 11.1 ? 0.1

= 111 cm/s

Time taken = 12 x 0.1 seconds

= 1.2 seconds

Acceleration = (111 cm/s – 0 cm/s) = 1.2 seconds

= 92.5 cm/s

Force = 3N

Acceleration = (final speed – start speed) ? time taken

Final speed = length of last five-dot strip ? time taken

Time Taken = number of five dot strips x 0.1 seconds

Final Speed = 17.3 ? 0.1

= 173 cm/s

Time taken = 8 x 0.1 seconds

= 0.8 seconds

Acceleration = (173 cm/s – 0 cm/s) ? 0.8 seconds

= 216.25 cm/s

Force = 5N

Acceleration = (final speed – start speed) ? time taken

Final speed = length of last five-dot strip ? time taken

Time Taken = number of five dot strips x 0.1 seconds

Final speed = 19.5 ? 0.1

= 195 cm/s

Time taken = 6 x 0.1 seconds

= 0.6 seconds

Acceleration = (195 cm/s – 0 cm/s) ? 0.6 seconds

= 325 cm/s

Force = 6N

Acceleration = (final speed – start speed) ? time taken

Final speed = length of last five-dot strip ? time taken

Time Taken = number of five dot strips x 0.1 seconds

Final speed = 19.9 ?0.1

= 199 cm/s

Time taken = 5 x 0.1 seconds

= 0.5 seconds

Acceleration = (199 cm/s – 0 cm/s) ? 0.5 seconds

= 398 cm/s

Force = 7N

Acceleration = (final speed – start speed) ? time taken

Final speed = length of last five-dot strip ? time taken

Time Taken = number of five dot strips x 0.1 seconds

Final speed = 22 ? 0.1

= 220 cm/s

Time taken = 6 x 0.1 seconds

= 0.6 seconds

Acceleration = (220 cm/s – 0 cm/s) ? 0.6 seconds

=366 cm/s

Force = 8N

Acceleration = (final speed – start speed) ? time taken

Final speed = length of last five-dot strip ? time taken

Time Taken = number of five dot strips x 0.1 seconds

Final speed = 20.5 ? 0.1

= 205 cm/s

Time taken = 5 x 0.1 seconds

= 0.5 seconds

Acceleration = (205 cm/s – 0 cm/s) ? 0.5

= 410 cm/s

Force = 9N

Acceleration = (final speed – start speed) ? time taken

Final speed = length of last five-dot strip ? time taken

Time Taken = number of five dot strips x 0.1 seconds

Final speed = 25 ? 0.1

= 250 cm/s

Time taken = 5 x 0.1 seconds

= 0.5 seconds

Acceleration = (250 cm/s – 0 cm/s) ? 0.5 seconds

= 500 cm/s

Force = 10N

Acceleration = (final speed – start speed) ? time taken

Final speed = length of last five-dot strip ? time taken

Time Taken = number of five dot strips x 0.1 seconds

Final speed = 24.6 ? 0.1

= 246 cm/s

Time taken = 5 x 0.1 seconds

= 0.5 seconds

Acceleration = (246 cm/s – 0 cm/s) ? 0.5 seconds

= 492 cm/s

Chart to show results

Force (Newton’s

Acceleration (cm/s)

1

98.3

2

92.5

3

216.25

4

5

325

6

398

7

366

8

410

9

500

10

492

(Originally I did not include the results to force 4N because I thought it would be interesting to see if I could predict the outcome using my graph. However it has become apparent that my graph is incorrect and this is no longer possible).

Graph

Conclusion

Unfortunately, my graph has not turned out how I expected. The results show me that in my experiment – the acceleration was not directly proportional to the force applied, which (in relation to my scientific research) should not be possible. The graph should be a straight diagonal line (as seen in my predicted graph) however mine was very varied, although it did follow a positive correlation, so we were on the right lines.

Evaluation

My results were not very accurate at all. I feel this is because there were a lot of factors that made it an unfair test despite my efforts to keep it fair. This could also be the reason why there are various anomalous results (it might be possible that all the results are anomalous!) The factors that would have altered my results include:

* Friction. The surface of the ramp caused friction because any type of grip on the surface could slow the trolley down. Also, the surface of the wheels could slow down the trolley because this is the affect of any type of traction provided by wheels. There is little we can do to create a “friction-less” workspace, but to keep it a fair test, we will keep the factors altering friction constant.

* Air-resistance. As the trolley moves through the air the trolley pushes on the air and the air pushes back on the trolley making it speed up less (this is called action and reaction). Again, there is not much we can do about this, but if we were to do this experiment again we would keep the aerodynamics of the trolley constant.

* Slight curve in runway. This makes a slightly bigger force act on the trolley as it goes downhill – therefore it has a greater speed. Next time, we could ensure that the runway is completely flat to prevent unfair alterations to results.

* The ticker timer would alter the result as well. Consider the fact that in every second the tape gets hit fifty times – this must have had some affect on the results. Unfortunately I don’t think we could change this were we to do the experiment again because with the equipment available to us – there is nothing more accurate.

Given more time, I would have liked to repeat each experiment up to five times, to ensure the results were fair -and to prevent the amount of anomalous results. Also, if I were to do it again, I feel that we could extend the experiment. Originally the aim was to find out the factors which affected acceleration. During this experiment we only altered the force and nothing else, it would be worthwhile to alter other things such as the mass of the trolley, the distance, the weight etc. It would be interesting to see if we could prove Newton’s Second Law through other experiments using different trolleys. (His law states that acceleration is directly proportional to the force applied). For example, we have proved (to the best of our ability) that through using the trolley that we did Newton’s Second Law does not work, but would it work for other trolleys?