Neco 2021 Physics Question 30

Practice objective / multiple choice question 30 from the 2021 Neco Physics examination.

Neco 2021 Physics Objective / Multiple Choice Hard Difficulty
Question 30 NECO • 2021 • PHYSICS • objective

A heated metal rod cools in air. The temperature (\(^\circ\)C) recorded every 20 s is: \(t\) (s): 0, 20, 40, 60, 80, 100; \(T\) (\(^\circ\)C): 120, 105, 93, 84, 77, 71. Assuming Newton's law of cooling \(T(t)=T_{\text{env}}+(T_0-T_{\text{env}})e^{-kt}\) with ambient temperature \(T_{\text{env}}=20^{\circ}\text{C}\), determine (a) the cooling constant \(k\) (to three significant figures), (b) the time required for the rod to reach \(30^{\circ}\text{C}\), and (c) the half‑life of the temperature difference (the time for \(T-T_{\text{env}}\) to halve).

Answer Options

A. k=6.20×10^{-3} s^{-1}; t_{30°C}=320 s; t_{1/2}=95 s
Correct Answer B. k=6.73×10^{-3} s^{-1}; t_{30°C}=342 s; t_{1/2}=103 s
C. k=7.15×10^{-3} s^{-1}; t_{30°C}=360 s; t_{1/2}=110 s
D. k=6.73×10^{-3} s^{-1}; t_{30°C}=300 s; t_{1/2}=120 s
Correct Answer
B
Correct Option:
k=6.73×10^{-3} s^{-1}; t_{30°C}=342 s; t_{1/2}=103 s

About This Question

This is Neco 2021 Physics Question 30. It is one of the objective questions from the 2021 Neco Physics examination.

Difficulty level: Hard .

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