Answer:
The mass of the Al-duckie should be 30 kg.
Explanation:
We will use the first law of thermodynamics:
ΔU = m·Cv·ΔT
Since the specific heat of water is 4.185 J(gºC), the change in the water's internal energy would be:
ΔU = 100 kg · 4.185 J(gºC) · (42ºC - 38ºC) = 1674 KJ
Given that no heat is lost, all the internal energy that the water loses while cooling down will transfer to the duckie. So, if the duckie has ΔU = 1674 KJ and its final temperature is the desired 38 ºC, we can calculate its mass using the first law again:
![m=\frac{\Delta{U}}{Cv{\Delta{T}}}=\frac{1674}{0.9*[38-(-24)]}=30Kg](https://tex.z-dn.net/?f=m%3D%5Cfrac%7B%5CDelta%7BU%7D%7D%7BCv%7B%5CDelta%7BT%7D%7D%7D%3D%5Cfrac%7B1674%7D%7B0.9%2A%5B38-%28-24%29%5D%7D%3D30Kg)
The silver coating on the inner bottle prevents heat transfer by radiation, and the vacuum between its double wall prevents heat moving by convection. The thinness of the glass walls stops heat entering or leaving the flask by conduction.
If you have no way to accurately measure all of the object's bumps and dimples, then the only way to measure its volume is by means of fluid displacement.
-- Put some water into a graduated (marked) container, read the amount of water, drop the object into the container, and read the new volume in the container. The volume of the object is the difference between the two readings.
-- Alternatively, stand an unmarked container in a large pan, and fill it to the brim. Slowly slowly lower the object into the unmarked container, while the pan catches the water that overflows from it. When the object is completely down in the container, carefully remove the container from the pan, and measure the volume of the water in the pan. It's equal to the volume of the object.
Answer:
★The second law of refraction
The ratio of sine of angle of incidence to the sine of angle of refraction is a constant for a light of given colour and for a given pair of media. This law is also called Snell's law of refraction. If 'i' is the angle of incidence and 'r' is the angle of refraction then, Sin i/Sin r = constant
This constant value is called the refractive index of the second medium with respect to the first.
Answer:
Time constant of RC circuit is 0.105 seconds.
Explanation:
It is given that,
Resistance, 
Capacitance, 
We need to find the expected time constant for this RC circuit. It can be calculated as :
So, the time constant for this RC circuit is 0.105 seconds. Hence, this is the required solution.
