Friday, 31 January 2014

Wild Chemistry Ride 4 (part 1):



Aim: To find out if a larger number of spokes will increase the time taken for the weight to be lifted to 15cm.
Hypothesis: The larger the number of spokes, the shorter the time taken to lift the weight to 15cm.

Independent Variable: the number of spokes

Dependent Variable: time taken for the weight to be lifted to 15cm

Controlled Variables: the mass of the weight, the length of the string from the wheel to the weight, size of each spoke, number of rotations of the sink handle thing

Assumptions: the speed of water flowing from the tap is consistent with every try, the (human error) reaction time is the same with every try

Materials Provided: (excluding the turbine and tower, though toilet rolls were given)


Procedure:
    1.  Cut out 5 3cmx5cm rectangles from the plastic board
2. Use tape to attach the rectangles onto the tape-coated part of the towel roll to create even spokes, then secure the spokes to the towel roll with plasticine
3. Poke a hole through the width of the end of the second towel roll
4. Stick a wooden skewer through the hole
5. Stick 2 sticks at the 15 cm mark to act as a stopper (distance between sticks < width of 5g weight
6. Poke a hole through the width of the end of the second towel roll
7. Stick a wooden skewer through the hole.
8. Stick two sticks at the 15 cm mark to act as a stopper
9. Tape one end of the string to the tape-coated end of the first towel roll
11. Stand the second roll up with the skewer at the top end
12. Secure the roll onto the bench
13. Guide the string from the first towel roll to over the skewer and between the two skewers below it
14. Tie the other end of the string to the weight
15. Position the turbine on the first roll horizontally across the sink and under the tap
16. Turn the tap on
17. Record the time taken for weight to be lifted to 15cm
18. Repeat 1-17 but make a 8-spoke turbine instead of a 5-spoke one

Video: one of our successful set-ups!


Data Tabulation:
Time taken for the load to be lifted 15cm when using 5 spokes/ms
Time taken for the load to be lifted 15cm when using 8 spokes/ms
Try 1
41
36
Try 2
30
38
Try 3
25
51
Average
32
42
*Note: We tested the reaction time by pressing the button three times and the result was 16ms for every try. Therefore 16ms was deducted from the time taken to derive the actual time taken for each try

Conclusion:
The smaller the number of spokes, the shorter the time taken for the weight to be lifted to the 15 cm mark.

Limitations:

We were not able to  
1. Control the speed of the water gushing out from the tap, which will affect the the speed of the turbine
2. Measure and ensure that the total mass of plasticine added to the spokes for the 1st and 2nd try were the same, due to time constraints
3. Measure the degree/distance between each spoke exactly due to time constraints

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