Answer:
The value of the average convection coefficient is 20 W/Km².
Explanation:
Given that,
For first object,
Characteristic length = 0.5 m
Surface temperature = 400 K
Atmospheric temperature = 300 K
Velocity = 25 m/s
Air velocity = 5 m/s
Characteristic length of second object = 2.5 m
We have same shape and density of both objects so the reynold number will be same,
We need to calculate the value of the average convection coefficient
Using formula of reynold number for both objects



Here, 


Put the value into the formula


Hence, The value of the average convection coefficient is 20 W/Km².
Answer:
The change in temperature, 
Explanation:
Given that,
The temperature in Spearfish, South Dakota, rose from
in just 2 minutes. We need to find the temperature change in Celsius degrees. Change in temperature is given by final temperature minus initial temperature such that,

The relation between degrees Celsius and degrees Fahrenheit is given by :

Here, F = 49 degrees

So, the change in temperature is 9.45 degree Celsius. Hence, this is the required solution.
Answer:
F = 3.20 N
Explanation:
Given:
Work done by child = 80.2 j
Distance that the car moves = 25.0 m
We need to find the force acting on the car.
Solution:
Using work done formula as.

Where:
W = Work done by any object.
F = Force (push or pull)
d = distance that the object moves.
Substitute
in work done formula.


F = 3.20 N
Therefore, force acting on the car F = 3.20 N