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2 Physics gcse MCQ

Q1) On a cold day a shiny metal feels colder to the touch than a black plastic rod. Which statement explains this observation?
A- The metal rod is a better absorber of infra-red radiation than the plastic rod
B- The metal rod is a better thermal conductor than the plastic rod
C- The metal rod is a worse absorber of Infra-red radiation than the plastic rod
D- The metal rod is a worse thermal conductor than the plastic rod
Why is the answer B here, yes Ik metals are good conductors and good absorbers of radiation but that doesn't explain why they feel cold if that's the case so why are C and D both wrong?

Q2)5 In an experiment, smoke particles are suspended in air and viewed through a microscope.
The smoke particles move about with short random movements.
Which of the following statements is correct?
A- Air particles have large masses compared to smoke particles and they move in one direction only.
B- Air particles have large masses compared to smoke particles and they move in random directions.
C- Air particles move at high speeds compared to smoke particles and they move in one direction only.
D- Air particles move at high speeds compared to smoke particles and they move in random directions.
The correct answer is D but how do you choose between B and D and why is B wrong?
Original post by Nasa1726
Q1) On a cold day a shiny metal feels colder to the touch than a black plastic rod. Which statement explains this observation?
A- The metal rod is a better absorber of infra-red radiation than the plastic rod
B- The metal rod is a better thermal conductor than the plastic rod
C- The metal rod is a worse absorber of Infra-red radiation than the plastic rod
D- The metal rod is a worse thermal conductor than the plastic rod
Why is the answer B here, yes Ik metals are good conductors and good absorbers of radiation but that doesn't explain why they feel cold if that's the case so why are C and D both wrong?

Q2)5 In an experiment, smoke particles are suspended in air and viewed through a microscope.
The smoke particles move about with short random movements.
Which of the following statements is correct?
A- Air particles have large masses compared to smoke particles and they move in one direction only.
B- Air particles have large masses compared to smoke particles and they move in random directions.
C- Air particles move at high speeds compared to smoke particles and they move in one direction only.
D- Air particles move at high speeds compared to smoke particles and they move in random directions.
The correct answer is D but how do you choose between B and D and why is B wrong?


Q1
It's not about the material being a good or bad absorber of radiation.
Though the black rod is a better absorber of radiation, it is also a better emitter.
But the question asks which statement explains the observation. Statement C is true but not the explanation of the observation.
The reason the rod feels cold to the touch is that heat is conducted into the rod from your finger very quickly.
This happens if the rod is a good thermal conductor. Statement B is correct and also the explanation.

Q2
B is wrong. Air particles (molecules of oxygen and nitrogen mainly) are not large compared to smoke particles. They are much smaller.
The air particles move much faster than the smoke particles and when they collide with the smoke they give it a little nudge.
(edited 1 year ago)
Reply 2
Original post by Stonebridge
Q1
It's not about the material being a good or bad absorber of radiation.
Though the black rod is a better absorber of radiation, it is also a better emitter.
But the question asks which statement explains the observation. Statement C is true but not the explanation of the observation.
The reason the rod feels cold to the touch is that heat is conducted into the rod from your finger very quickly.
This happens if the rod is a good thermal conductor. Statement B is correct and also the explanation.

Q2
B is wrong. Air particles (molecules of oxygen and nitrogen mainly) are not large compared to smoke particles. They are much smaller.
The air particles move much faster than the smoke particles and when they collide with the smoke they give it a little nudge.

ahh okay I get itt thank you smm!

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