Certain quantity of water cools from 70⁰ C to 60⁰C in the first 5 minutes and to 54⁰C

Certain Quantity Of Water Cools From 70 C To 60c Physics Question

Certain quantity of water cools from 70⁰ C to 60⁰C in the first 5 minutes and to 54⁰ C in the next 5 minutes. The temperature of the surroundings is

Options

(a) 45⁰ C
(b) 20⁰ C
(c) 42⁰ C
(d) 10⁰ C

Correct Answer:

45⁰ C

Explanation:

Let the temperature of surroundings be θ₀
By Newton’s law of cooling
(θ₁ – θ₂ / t) = k [(θ₁ – θ₂ / 2) – θ₀]
[(70 – 60) / 5] = k [(70 + 60 / 2) – θ₀] ⇒ 2 = k [65 – θ₀] ——(i)
Similarly, (60 – 54) / 5 = k = [(60 + 54 / 2) – θ₀]
6 / 5 = k [57 – θ₀] ——–(ii)
By dividing (i) by (ii) we have
10 / 6 = (65 – θ₀) / (57 – θ₀) ⇒ θ₀ = 45⁰

Related Questions:

  1. A galvanometer of 50 Ω resistance has 25 divisions. A current of 4×10⁻⁴ A gives
  2. The rate of increase of thermo-e.m.f. with temperature at the neutral temperature
  3. The work of 146 kJ is performed in order to compress one kilo mole fo gas adiabatically
  4. Maximum velocity of the photoelectron emitted by a metal is 1.8×10⁶ ms⁻¹.
  5. All components of the electromagnetic spectrum in vacuum have the same

Topics: Properties of Bulk Matter (130)
Subject: Physics (2479)

Important MCQs Based on Medical Entrance Examinations To Improve Your NEET Score

18000+ students are using NEETLab to improve their score. What about you?

Solve Previous Year MCQs, Mock Tests, Topicwise Practice Tests, Identify Weak Topics, Formula Flash cards and much more is available in NEETLab Android App to improve your NEET score.

NEETLab Mobile App

Share this page with your friends

Be the first to comment

Leave a Reply

Your email address will not be published.


*