From looking at the graphs the line of best fit seems to go through all of them well, showing that there is a steady increase and that there are no drastic changes in stopping distance or kinetic energy used.
The trend shown by my graphs are that as the Kinetic energy goes up the stopping distance goes up. Also if the kinetic energy is under 1.0 the stopping distance generally seems to be 4/6 metres. If the kinetic energy is 1.5 or below the stopping distance is around 6/8 metres. If the kinetic energy is 2.0 or below or around that area of KE then the stopping distance works out to be around 10/12 metres.
The prediction that the braking distance of a car or bicycle depends upon the kinetic energy it has before the brakes are applied is true. This is because the stopping distance can vary due to the velocity and kinetic energy. If the velocity is fast then the stopping distance will be further, this is because there will be more kinetic energy the more force will need to be exerted into the brakes to stop. We can work out the work done by doing an easy sum – force x distance. The greater the kinetic energy the greater the force of distance must be. The main trend that can be found is the one that tells you that if you double the velocity the KE gets four times bigger - v² = KE x 4 >.
The prediction the students set was correct, the stopping distance of the bicycle depends upon the kinetic energy it has just before the brakes are applied. But some of the kinetic energy goes through a energy change and a small amount is used up by small things, such as:-
- Heat – Friction on the brake pads rubbing on the wheel, causing heat.
- Sound – From the brake pads rubbing on the edge of the wheel.
- Friction – From the brake pads grasping onto the wheel edge.
Evaluation:- The experiment went well, I think the test was carried out well although I think a few things could be changed, and I will outline those points in my evaluation. The results that were produced were what was expected – that as the kinetic energy went up the stopping distance went up with it.
I found one anomalous result on the 80 kg rider’s range bar graph, This may have been because the students record that they took wasn’t accurate or the student was going at the wrong velocity.
There are a few improvements that could be made to the experiment, the students could have had the person who was cycling to take down the time of how long it took, because he could see when to start timing better. Or the students could have used light gates to measure the velocity more accurately, or use and police speed gun to get an accurate result. They could have used the same person to ride the bike each time to get more of a variation of one riders time.
From the range bars I can see that most of the results were accurate, apart from one anomalous result (labelled on diagram). The line on the range bars is nicely curved showing a gradual drop in speed.
Another way of conducting the experiment would be to use a car, as you could set up velocity meters in it, and the readings could be much more accurate for the time.