When I find out the amount of weights I need in order for the tub to not turn over, I can begin my experiment. I will tape in the weights and pull the elastic band back to where I measured 2N. I will put the margarine tub where I pulled the band back and let go of the band. I will then measure where the tub stops. I then record my results and repeat the experiment another two times for more accurate results.
I then measure 10 newtons, by pulling the elastic band back using the newton measure and mark out 10N using the chalk. I use the same weights as I know that the tub will not turn over when in motion. I will put the margarine tub against the elastic band and let go. I will measure where the tub stops using a metre long ruler. I will record my results and repeat the experiment another two more times for more accurate results.
Detailed Method
In my experiment there are a number of factors that will effect my investigation. The variable factors are the force of the band, mass of the tub, surface area of the front of the tub, surface area of the bottom of the tub, floor surface and the tub shape.
I will be trying to prove my prediction that the greater the force applied to the tub, the bigger the distance it will travel, as a result of this I will be measuring the distance the tub travels when a force of 2 newtons and 10 newtons are applied to the tub. For this reason the only variable factor in my experiment that I will be changing is the force in the elastic band.
I am going to repeat my experiment three times. Therefore to keep the experiment a fair test I will have to keep some of the variable factors the same. The variable factors of my experiment that I will not change are the mass of the tub, surface area of the front of the tub, surface area of the bottom of the tub, floor surface and the tub shape.
If I didn’t control the mass of the tub each time I did the experiment then it wouldn’t be a fair test and I am trying to prove that force changes the distance the tub travels not the mass of the tub. If I decreased the mass of the tub next time I repeated the experiment then the acceleration would decrease, so would the speed. Resulting in the distance the tub travels also decreasing compared to when the mass was greater in the pervious experiment.
To keep the investigation a fair test and to make sure I am only testing that the force applied to the tub affects the distance it travels, I must keep the surface area of the front of the tub the same. This is because if I increased the surface area next time I did the experiment then the air resistance would increase, because more air particles collide with the tub. Meaning that the distance the tub travels decreases because air resistance has increased.
If I changed the surface area of the bottom of the tub then the amount of friction slowing the tub down would increase. This is because there is a rougher surface catching a rough floor surface. Therefore the tub wouldn’t gain a lot of speed and the distance it travels would be low. By keeping the surface area of the bottom of the tub the same I am keeping the experiment a fair test and making sure that I am only proving that the greater the force applied to the tub, the greater the distance it will go.
By changing the surface that I am doing the investigation on I could be changing the amount of friction being produced between the surface and tub. If I did one experiment on a rough surface then the distance would lower, then that if I did the experiment on a smoother surface. To keep the experiment a fair test I want to produce the same amount of friction so I would keep the surface the same every time I repeated the investigation.
To keep the experiment fair and to establish that the bigger the force applied to the tub the greater the distance it will travel I will keep the shape of the tub the same. If I changed the shape of the tub then I am altering the aerodynamic nature of the tub. This means that there could be more or less air particles going by the tub then in the previous experiment. If there are more air particles colliding with the front of the tub then this mean that air resistance has been increased. If air resistance has been increased then the distance the tub travels will decrease as air resistance is a force slowing the tub down, and decreasing the distance it travels.
Preliminary Investigation
Aim: To determine the range of forces to be used and to decide the values of the other variables.
Shape of tub: Pure
Surface area of base: 82cm²
Surface area of front of tub: 42cm²
Mass of the tub (including 4 weights): 56.3g
Floor surface used: Floor
Distance traveled at 2N: 16cm
Distance traveled at 10N: 261cm
Force range to be used: 2N – 10N
A Table To Show How Changing The Force On A Elastic Band Affects The Distance A Tub Travels
I added another row to my table as I had an anomalous result. This means that the 8 N force did not fit neatly onto the graph when I plotted my results. So I re-did the experiment and I recorded my results and plotted the new average of 254.3 cm onto the graph. This was a much closer result and it became the improved result.
Conclusion
Whilst carrying out my experiment I found out that the greater the force I applied to the tub the further the margarine tub travelled. This is what I predicted. Therefore my prediction was correct.
An increase in force resulted to an increase in the tub travelling a further distance due to energy and forces.
The greater the energy applied to the tub, the further the tub travels. This is because the tension in the band increases the more you pull it back. Therefore potential energy and kinetic energy are transferred to kinetic energy in the tub. The tub gains the energy and it travels a further distance until forces are dominant over energy. Hence the more energy applied to the tub through pulling the band back more, the bigger the distance the tub travels.
When the elastic band is pulled back the tub will travel a further distance the greater the force applied to the margarine tub. This is because acceleration is increased due to the force getting bigger. The tub then gains speed and the tub will travel a greater distance due to higher amounts of force on the tub. The tub then stops when air resistance and friction are overriding the force of the tub.
After plotting my results I joined them up and achieved a straight line but I did not go through the origin. This is not what I expected. I expected that you would have got a straight line that did go through the origin. I expected a straight line because of Newtons 2nd law of motion. Force = Mass x Acceleration tells us that the force applied to the tub is proportional to the acceleration of the tub. I thought that I would also get a straight line because of the equation Speed = Distance ÷ Time reveals that distance is proportional to speed. Acceleration = Speed Change ÷ Time tells me that speed change is proportional to acceleration which also indicates to that I should have got a straight line graph going through the origin.
From these equations and ideas I can declare that force in the elastic band is proportional to the distance ht tub travels. If this was true then I should have got a straight line graph of force against distance which would have gone through the origin. As I didn’t get this then it means that the modal must be more complex then I actually used.
There a few problems which could have lead to me not accomplishing my straight line graph going through the origin. One problem could have been that I didn’t take into account the counter force when the band moves. So, the force acting on the tub will always be less then we think because counter force is acting on the band slowing it down when it is pushing the elastic band. Another problem is that the force on the band decreases as it goes back to its original potion. The tub would not have been in contact with the band for the same period of time which would lead to the tub either travelling a further or lesser distance then it would have, if in contact for same period of time as the previous experiment. I didn’t let the tub travel for the same time every time I did the investigation. I just assumed that the tub travels for the same length of time. Therefore as the speed increases the time the tub travels increases. For all these reasons the modal is more complex then we expected as the relationship between the force and the distance is not proportional, as the line in the graph does not go through the origin, which is shown through the shape of the graph.
Evaluation
After doing my investigation I found out that the greater the force applied to the tub the bigger the distance it travelled, so I was able to solve my problem as my experiment was successful.
There could be a number of errors within my results. The evidence to show is this that I got an anomalous result. I also never got the same distance when I repeated the experiment at the same force, and I had to re-do the force on the tub more then three times to get a range of five or less. If my experiment was accurate then I would not have got an anomalous result, I would have got the same distance every time I did the experiment at a force and I wouldn’t have got a range as the distances would all be the same at that particular force, resulting in a straight line graph going through the origin.
There are many procedural problems that I came across in my experiment. As I pull the elastic band it loses tension. This would result in less force being produced and the distance that the tub actually travels would be less. If I could do the experiment again then I would measure the force every time I repeated the experiment, instead of pulling the band back to the mark and letting it go from there.
Another problem that occurred was that the tub wasn’t always in the middle of the band. This would result in an increase or decrease on the force on the tub. If the force increases then the distance of the tub increases and if the force decreases then the distance is reduced. If I could re-do the investigation then I would mark out the centre of the center of the band and place the tub there every time I did the experiment.
A problem that I came across during my experiment was that the position of the chair changed when I did the experiment the next day or with a different force if the chair moved. As a result the force on the tub would be greater or lesser then what it should be. As a consequence the distance would be bigger if the force was greater and smaller if the force was lesser. An improvement that I could make on this problem if I did do the investigation again is would mark around the legs and maybe add weights to the chair so that it didn’t move and then check that the markings where still visible.
Human error could also have affected my experiment. This would result to an increase or decrease in the force applied to the tub. The distance of the tub would then increase if the force on the tub was amplified, and decline if the force decreased. If I did do the investigation again then I would concentrate more so that I didn’t make any errors.
As I did the experiment over a period of two days would affect any problems that aroused during the investigation. This is because the surface would either be dirtier or cleaner then when I did the experiment the before. If the floor was dirtier then before the amount of friction produced would increase and the distance then tub travels would be less. However, if the floor was cleaner then in the previous day the amount of friction between the surface and tub would be less and the margarine tub would travel a much further distance. If I could repeat the investigation then I would clean the floor each time I did the experiment to make sure that the amount of friction between the surface and tub was even each time I did the investigation.
Since the tub did not travel in a straight line the distance the tub travels for that force would be less as my measurements would not be accurate. This is because I measured from the back of the tub and drew a line from the back across the floor to the ruler. If I did the experiment again then I would measure from the point the tub left the band to the tub, even if it meant measuring diagonally.
A procedural problem that would have affected my results would be an increase or decrease of air resistance that would have been achieved from the door or window being open or shut. The consequence of having the door or window open would be an increase in distance if the air resistance was low because the door or window was shut. If the door or window was open then there would be an increase in air resistance resulting to the tub travelling a smaller distance. I would keep the doors and windows shut if I did the investigation again.
The position on the floor where I placed the chair when I did the experiment the next day would be different to the previous day. The affect it would have on my investigation is that the friction levels will be different as the floor is straighter in other parts. If friction is increased then the distance the tub travels will increase. The tub will travel a smaller distance with high amounts of friction. I would mark around the legs of the chair on the floor where I place the chair in the experiment if I could do the investigation again.
The mass of the tub would be different due to using different weights the next day, would cause a problem. This is as the mass amplifies then the distance decreases. If the mass is decreased then the distance of the tub increases. If I did the investigation again then I would use the same weights and then check that the tub and weights weighed the same as the experiment before.
The distance was affected by the tub lifting into the air when it was forced forward by the elastic band. The amount of friction was therefore decreased and the distance that the margarine tub travelled was greater then it should have been. If I could re-do my investigation then I would do that attempt of the force again.
