Year 7 Science · Unit 3 · Lesson 9
Challenge Worksheet
Learning Goals
Find the mistake
A student wrote this experimental report
"To measure friction between a wooden block and three different surfaces (smooth tile, sandpaper, and carpet), I attached a spring scale to each block and pulled it. I didn't bother zeroing the scale first because it looked close to zero. I pulled the spring scale at an angle — about 30 degrees upward from the horizontal — because that felt more comfortable. I read the scale from above, looking down at the pointer from a standing position. I only tested each surface once because I ran out of time. My results showed the carpet had the lowest friction of all three surfaces."
1. List ALL the errors you can find in this student's procedure. For each error, write the name of the mistake clearly.
2. For each error you found, explain its specific effect on the measurement result — did it make the reading too high, too low, or unreliable? Explain your reasoning.
3. Considering the errors you found, explain why the student's conclusion that "carpet had the lowest friction" may not be reliable. What would need to be done differently to trust the results?
1. An AFL scientist at the Gabba in Brisbane uses a force sensor (measuring in Newtons) to measure the kick force of a forward during training. The sensor is attached horizontally at ankle height. The player kicks at an upward angle of 45 degrees. Explain two reasons why the force sensor reading may not accurately represent the true kicking force in this setup. What adjustments would improve the measurement?
2. A student claims: "Hooke's Law means that if I keep adding more and more weights to a spring, the extension will keep doubling every time I double the force — forever." Identify the flaw in this claim and explain the scientific concept that limits Hooke's Law. What would you observe when this limit is reached?
Wrap Up
In one sentence, what was the main idea of this lesson?