Your opinion on how to interpret a problem

  • Thread starter Thread starter Phys O
  • Start date Start date
AI Thread Summary
The discussion centers on a vague homework problem that asks students to calculate a property of two objects and determine "how much more" one object is compared to the other. The original poster, a TA, recalls being penalized for interpreting the question as asking for a difference, while the correct interpretation was to calculate a ratio. Now in a grading position, the TA plans to award full credit for those who calculate the difference, acknowledging the ambiguity in the wording. Other participants suggest that the context of the problem may clarify the expected answer, and recommend consulting the course professor for guidance. Ultimately, the consensus leans toward accepting both interpretations to accommodate varying student responses.
Phys O
Messages
2
Reaction score
0
I'm grading some homework (I'm a TA) and one of the word problems is rather vague. The problem is very short, it asks one to calculate a property of two objects, and then asks "how much more" for one of the objects.

When I took the class I considered this as asking for the difference between quantity A and B. The TA when I took the class end up taking off 40% of what the problem was worth. The correct answer was to calculate a ratio. The wording, in my opinion, was too vague, and for me, when someone asks "how much more" one object is with regard to another, that's asking for a difference of some sort.

Now that I'm in the TA position, I don't necessarily want to punish people for interpreting problem like I originally did. I'm going to give full credit for anyone that calculated a the difference correctly regardless of what anyone posts here. Indeed, by the time anyone replies the homework will be graded and out of my hands.

So, just curious, how would any of you handle this?
 
Physics news on Phys.org
IMO it seems vague to me as well. I would do what you plan to do unless specific instruction was given in class.
 
Phys O said:
I'm grading some homework (I'm a TA) and one of the word problems is rather vague. The problem is very short, it asks one to calculate a property of two objects, and then asks "how much more" for one of the objects.

When I took the class I considered this as asking for the difference between quantity A and B. The TA when I took the class end up taking off 40% of what the problem was worth. The correct answer was to calculate a ratio. The wording, in my opinion, was too vague, and for me, when someone asks "how much more" one object is with regard to another, that's asking for a difference of some sort.

Now that I'm in the TA position, I don't necessarily want to punish people for interpreting problem like I originally did. I'm going to give full credit for anyone that calculated a the difference correctly regardless of what anyone posts here. Indeed, by the time anyone replies the homework will be graded and out of my hands.

So, just curious, how would any of you handle this?

Your original description of the problem did not refer to the word difference [which implies subtraction].
Expressing an increase as a factor or percentage increase is by far the most common.

For example, suppose you have a wire of given resistance, then another is made from wire whose resistivity is 0.1 more, it is 1 metre longer and 0.5 mm thicker. What will be the resistance of the new wire?

Where as if the resistivity is 130% greater, it is 12.5% longer and 20% thicker ...

As a stand alone queston, there may be some ambiguity, but in the context of the other questions involved, the type of answer should be obvious. If I were a student, I would be saying "that's an increase of 47.5 or 12%" to cover both bases.

EDIT: I would be interested in seeing the exact wording of the question you refer to.
 
I would consult with the course professor, and explain your reasoning. It might be best to accept either form of answer.
 
Thread 'Variable mass system : water sprayed into a moving container'
Starting with the mass considerations #m(t)# is mass of water #M_{c}# mass of container and #M(t)# mass of total system $$M(t) = M_{C} + m(t)$$ $$\Rightarrow \frac{dM(t)}{dt} = \frac{dm(t)}{dt}$$ $$P_i = Mv + u \, dm$$ $$P_f = (M + dm)(v + dv)$$ $$\Delta P = M \, dv + (v - u) \, dm$$ $$F = \frac{dP}{dt} = M \frac{dv}{dt} + (v - u) \frac{dm}{dt}$$ $$F = u \frac{dm}{dt} = \rho A u^2$$ from conservation of momentum , the cannon recoils with the same force which it applies. $$\quad \frac{dm}{dt}...
TL;DR Summary: I came across this question from a Sri Lankan A-level textbook. Question - An ice cube with a length of 10 cm is immersed in water at 0 °C. An observer observes the ice cube from the water, and it seems to be 7.75 cm long. If the refractive index of water is 4/3, find the height of the ice cube immersed in the water. I could not understand how the apparent height of the ice cube in the water depends on the height of the ice cube immersed in the water. Does anyone have an...
Back
Top