Investigate the factors which affects the distance travelled by a tub propelled by an elastic band.

Planning

Aim: To find out how far a tub can travel by changing factors, which affect it. In this investigation the variables that affects the distances and is changed is mass that is applied on the tub while increasing the mass of the tub.

Other variables include:

The surface on which the tub is propelled on as some surfaces creates more friction than others. Friction is the force produced when two surfaces rub on each other. Some surfaces produce more friction and so try to prevent the two surfaces from sliding over each. This means that the force stops the tub from travelling far. The greater the friction the shorter the distance is it travels. Smoother surfaces allow the tub to travel further and since the tub is smooth the other surface also needs to be smooth as well in order to do this.

The size of the elastic band, as bigger and thicker bands are more elastic than smaller and thinner ones. Because they are more elastic the band can be stretched more so that the elastic band stores more potential energy and when the tub is released the energy is transferred from elastic band into the tub and the energy changes into kinetic energy as the tub travels forward. Bigger elastic bands can store more potential energy than small ones.

The force, which is applied onto the elastic band. A greater force means a greater distance, because there is more potential energy as the energy is transferred from the hand to the band and then to the tub. The further the band is pulled back the more force is used and so the tub would travel further than when a small force is used.

In this experiment the factor that is changed is the mass of the tub and the force is kept. Then the force is changed but kept constant while the mass is increased. This is related to the formula of

Force in N= mass in kg x acceleration in m/s2

Preliminary work:

Before doing the actual experiment we tried out different methods to propel the tub. First we used two stools and put an elastic band on one foot on each stool. The elastic band was put around the edge of the tub so that the tub was inside the band. The band was twisted by rotating the tub and then we it was released. The result was that it flew upwards and then forwards. The more it was twisted the further the tub should have gone however the tub was released from the band. Also this wasn’t a good method to measure the distance the tub travelled, as we would need to do more unnecessary measurements. This meant we couldn’t use this technique.

We adapted the set so that instead flying upwards it would slide along the floor. The other change was to catapult rather than twisting as we could measure the distance it travelled.

Equipment List

Stool

2 fat elastic bands

Tub

Newton meter

10g weights

Ruler

Scale

Method

A hole is made in the tub
An elastic band is cut and then thread through the hole
A knot in the elastic band on the inside of the tub so it can’t fall out.
A Newton metre is attached to ...

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We adapted the set so that instead flying upwards it would slide along the floor. The other change was to catapult rather than twisting as we could measure the distance it travelled.

Equipment List

Stool

2 fat elastic bands

Tub

Newton meter

10g weights

Ruler

Scale

Method

A hole is made in the tub
An elastic band is cut and then thread through the hole
A knot in the elastic band on the inside of the tub so it can’t fall out.
A Newton metre is attached to the elastic band, which is attached to the tub. The Newton metre measurer the force applied onto the elastic
Then the empty tub along with the elastic band and the Newton metre is weighed on the scale.
The weight recorded.
Another elastic band is cut and then each end is tied to a foot on a stool. The distance between the elastic band and the floor is 40mm.
The tub is placed on the floor, which is a non-skid floor, which means it’s not slippery. This shows that there will be more friction between the floor and the tub.
Then the tub is pulled back using the Newton meter until it reads 15 Newtons. Meanwhile another person sits on the stool to stop it from moving.
The Newton meter is released with the tub facing upwards and the tub should travel along the floor, making sure that no one stands in front of the experiment or walk across before releasing it for safety reasons. Also the person pulling back the tub and releasing it should be the same person.
When the tub stops the distance between the back edge and the back feet of the stool is measured using the ruler. The result is recorded.
This is repeated 3 times to calculate an average and to make sure that the result are reliable. This helps to detect any anomalies.
Then the weights are put in using the 10g slotted masses starting with 2 10g slotted masses.
The slotted masses are stuck in using tape and blue tack, which would add more mass
The tub is weighed and because the masses are placed in the centre of the tub so all the weight will be in the centre.
This then catapulted always repeating it 3 times
More weights are added each time using the same process until there are 8 10g masses in the tub
Then the force is changed to 10 Newtons and increasing the mass each time until there are 8 10g masses.

Prediction

I predict that the tub will travel further if the elastic band is pulled further applying more force and if there less mass. This is because there is more energy in the elastic band if there is a greater force so that more energy is transferred into the tub. More mass means it’s going to travel a shorter distance because of inertia, which is the principle of more mass means a greater resistance of moving.

Obtaining evidence

Analysing and considering evidence

Both graphs and tables show that as the mass increases so the distance decreases through the line of best fit.

The tables show that if the force is increased the distance increases as well.

However the results that the tub will travel further if a greater force is used while the mass is increased. The graph showing the relationship between the mass of the tub and the distance travelled using a 15 N force shows the decrease in distance when mass increases because when the mass is 62g the average distance the tub travels is 3.76m, however when the mass is 1.4g the average distance is 1.75m and the distance decreases even more when the mass is 1.46g and the tub travels 0.91m. The graph also shows a fast decrease because the gradient of the line of best fit is steep. Even though the line is a little bit curved it still shows a steady decrease. As the mass doubles the distance is reduced by a factor of about 3.

The graph showing the relationship between the mass of the tub and the distance it travels using 10N also shows the decrease because when the mass is 63g the average distance is 1.39m whereas when the mass of the tub is 146g the tub travels 0.43m. It shows an even faster decrease than the other graph because it’s steeper. The line is straighter which means the decrease is more even. The graph also shows that when the mass doubles the distance halves. This shows the fact that mass is inversely proportional to the distance. This graph displays this better than the on where the tub used a mass of 15N.

The reason for this is because of inertia, which is the effect of resisting acceleration and if an object doesn’t accelerate much then it won’t travel far. As mass increases so the greater inertia is so the more it resist acceleration and therefore travelling a shorter distance. This is what happens with the tub. More masses are put in increasing the total mass of the tub and so increasing the inertia, which act on it, allowing the tube not to accelerate as much and so it will resist velocity more.

The results show that tub, which had 15N, travelled a longer distance than the one that was pulled with 10N, because when the tub weighed 63g and a force of 15 N was used the distance it travelled was 3.76m, but when a force of 10N was used when the tub weighed 63g the distance was 1.39m. When the mass of the tub was 146g and the force was 15N the distance it travelled was 0.91m however when a 10N force was applied the distance was only 0.43m.This shows that force and distance are proportional, because when the force increases by a one and a fifth the distance doubles.

The reason for this is that there is a greater force, which means there is more energy transferred in the tub as kinetic energy from the elastic band. Also the tub has a greater forward for with 15 N than with 10N which means that the opposite force air resistance is going to be less with the tub travelling with a force of 15N than with the tub travelling with 10N. This means that the forces are more unbalanced with the tub travelling with a force of 15N. So the tub will accelerate more and travel a longer distance than the tub with 10N

The conclusion supports the prediction made at the beginning because the results prove that when the mass is increased so distance increases.

The reasons for this give a valid explanation as to why this occurs. The conclusion proved that a greater mass means a shorter distance , but a greater force means a greater distance.

Evaluation

The results that were obtained were quite reliable as they showed what they were meant to show and so prove the prediction. Even though the results are not exact they are still close which also include anomalies. The graph showing the relationship between the mass of the tub and the distance using a force of 15 N shows a main anomaly, however it’s not completely irregular which means there was an error however it didn’t affect the analysis of the results. The results were able enough to support the conclusion only to an extent because its apparent that there are some irregularities which although supported the basic facts of the conclusion but not the detailed ones, such as if mass and distance were proportional, because it was difficult to find an obvious connection between them.

The procedure itself was a good way to show how the distance changes when the mass is varied and the differences between the distances made it clear that there was a decrease. It was a simple procedure with simple equipment, which gave the correct results and achieved what we aimed to do. It was a quick experiment, which meant we had time to do more variations such as putting more slotted masses and changing the force and so do more sets of results. The procedure was safe because there weren’t many hazards involved such being hurt by the tub as it travel along the floor and the equipment was safe to use. It also allowed the tub to travel far especially with the usage of the Newton meter at the back. Also the reason, which could explain the anomalies, could be that the tub had to carry more load apart from the mass itself but also the other elastic band the Newton meter, which was also heavy. Because the Newton meter was attached at the back this caused some problems as the tub would sometimes skid on the Newton meter by lying on top of it as it travels and so it would travel a shorter distance because the Newton meter is making the tub stop at the wrong time so that the reading would be wrong. Repeating it three times though still gave us accurate results as they were all were similar. However a change that could be made would be removing the Newton meter, as then the tub would carry so as many loads, which could create wrong results. Another change would be spreading the slotted mass evenly out as we put them in the centre which means all the weight was in the centre instead of being evenly spread along the tub. This would have given better results as position the masses in one place could affect how far the tub travels.

Further work to this investigation could include using different sizes of bands and observing which size enables the tub to travel further. Also different surfaces could be used such as carpet or a surface that is very smooth such as ice if that is available, because this will create very little friction and so would be a contrast to a surface such as the one used in this experiment.