## Jaweria Group Title Please anyone help me!! one year ago one year ago

1. Jaweria Group Title

When a cold drink is taken from a refrigerator, its temperature is 5°C. After 25 minutes in a 20°C room its temperature has increased to 10°C. (a) What is the temperature of the drink after 50C minutes? (b) When will its temperature be 15°C?

2. Cha1234 Group Title
3. chrismoon Group Title

@Cha1234 That question is asking for different values.

4. Jaweria Group Title

but this site has really confused answer

5. Jaweria Group Title

can anyone explain this to me here?

6. chrismoon Group Title

I learned this in basic physics, I assume solving the same way. Have you been taught Newton's Law of Cooling?$\frac{ dT }{ dt }=k(T-20)$

7. Jaweria Group Title

can anyone explain this to me that how I m getting this answer ln[(20 - T)/(20 - 5)] = - 0.01622

8. Jaweria Group Title

when I m calculating it I m getting 1.10623

9. satellite73 Group Title

don't make it so hard it is easier than you think

10. satellite73 Group Title

When a cold drink is taken from a refrigerator, its temperature is 5°C. After 25 minutes in a 20°C room its temperature has increased to 10°C. (a) What is the temperature of the drink after 50C minutes? (b) When will its temperature be 15°C?

11. satellite73 Group Title

work with the differences in the temperature, that is what decays to zero initial difference is $$20-5=15$$ degrees, after 25 minutes the difference is $$10-20=10$$ degrees so the difference has decreased by $$\frac{10}{15}=\frac{2}{3}$$

12. satellite73 Group Title

i.e. every 25 minutes, the difference in the temperature decreases by $$\frac{2}{3}$$ starting with an initial difference of $$15$$ you can model this by $15\left(\frac{2}{3}\right)^{\frac{t}{25}}$

13. satellite73 Group Title

after another 25 minutes, at 50 minutes, it will decrease by another $$\frac{2}{3}$$ from $$10$$ to $$10\times \frac{2}{3}=\frac{20}{3}=6\tfrac{2}{3}$$

14. satellite73 Group Title

that of course means it is $$6\tfrac{2}{3}$$ colder than the 20 degree room, so its temperature is $$20-6\tfrac{2}{3}=13\tfrac{1}{3}$$

15. satellite73 Group Title

b) when will it be 15 degrees? that means b) when will it be 5 degrees colder than the room set $15\left(\frac{2}{3}\right)^{\frac{t}{25}}=5$ and solve for $$t$$