To remove magnesium oxide layer from the ribbon which may prevent or slow down the burning of magnesium ribbon.
Gold is the best pure substance. The answer is gold
<span>conductor because it conducts the electrons</span><span />
The average speed :
1. 10.44 m/s
2. 10.42 m/s
3. 9.26 m/s
The distance 100 m have the greatest average speed
<h3>Further explanation
</h3>
Given
Distance and time of runner
Required
Average speed
Solution
<em>
Average speed : total distance : total time
</em>
1. d = 100 m, t = 9.58 s
Average speed : 100 : 9.58 = 10.44 m/s
2. d=200 m, t=19.19 s
Average speed : 200 : 19.19 = 10.42 m/s
3. d=400 m, t = 43.18 s
Average speed : 400 : 43.18 = 9.26 m/s
The distance 100 m have the greatest average speed
