Answer:
The net amount of energy change of the air in the room during a 10-min period is 120 KJ.
Explanation:
Given that
Heat loss from room (Q)= 60 KJ/min
Work supplied to the room(W) = 1.2 KW = 1.2 KJ/s
We know that 1 W = 1 J/s
Sign convention for heat and work:
1. If heat is added to the system then it is taken as positive and if heat is rejected from the system then it is taken as negative.
2. If work is done by the system then it is taken as positive and if work is done on the system then it is taken as negative.
So
Q = -60 KJ/min
In 10 min Q = -600 KJ
W = -1.2 KJ/s
We know that
1 min = 60 s
10 min = 600 s
So W = -1.2 x 600 KJ
W = -720 KJ
WE know that ,first law of thermodynamics
Q = W + ΔU
-600 = - 720 + ΔU
ΔU = 120 KJ
The net amount of energy change of the air in the room during a 10-min period is 120 KJ.
Answer:
see explaination
Explanation:
import java.util.InputMismatchException;
import java.util.Scanner;
public class calculate {
static float a=0,b=0;
double cal()
{
if(a==0||b==0)
{
System.out.println("no values found in a or b");
start();
}
double x=(a*a)+(b*b);
double h=Math.sqrt(x);
a=0;
b=0;
return h;
}
float enter()
{
float val=0;
try
{
System.out.println("Enter side");
Scanner sc1 = new Scanner(System.in);
val = sc1.nextFloat();
return val;
}
catch(InputMismatchException e)
{
System.out.println("Enter correct value");
}
return val;
}
void start()
{
calculate c=new calculate();
while(true)
{
System.out.println("Enter Command");
Scanner sc = new Scanner(System.in);
String input = sc.nextLine();
switch(input)
{
case "A":
a=c.enter();
break;
case "B":
b=c.enter();
break;
case "C":
double res=c.cal();
System.out.println("Hypotenuse is : "+res);
break;
case "Q":
System.exit(0);
default:System.out.println("wrong command");
}
}
}
public static void main(String[] args) {
calculate c=new calculate();
c.start();
}
}
Answer:
E = 2940 J
Explanation:
It is given that,
Mass, m = 12 kg
Position at which the object is placed, h = 25 m
We need to find the potential energy of the mass. It is given by the formula as follows :
E = mgh
g is acceleration due to gravity
So, the potential energy of the mass is 2940 J.
Answer:
14.52 minutes
<u>OR</u>
14 minutes and 31 seconds
Explanation:
Let's first start by mentioning the specific heat of air at constant volume. We consider constant volume and NOT constant pressure because the volume of the room remains constant while pressure may vary.
Specific heat at constant volume at 27°C = 0.718 kJ/kg*K
Initial temperature of room (in kelvin) = 283.15 K
Final temperature (required) of room = 293.15 K
Mass of air in room= volume * density= (4 * 5 * 7) * (1.204 kg/m3) = 168.56kg
Heat required at constant volume: 0.718 * (change in temp) * (mass of air)
Heat required = 0.718 * (293.15 - 283.15) * (168.56) = 1,210.26 kJ
Time taken for temperature rise: heat required / (rate of heat change)
Where rate of heat change = 10000 - 5000 = 5000 kJ/hr
Time taken = 1210.26 / 5000 = 0.24205 hours
Converted to minutes = 0.24205 * 60 = 14.52 minutes
