During testing, the team records a surface heat flux of 7.2 million W/m². 

Additional Information: 

• The base heat flux without aluminium is 6.0 million W/m². 

• The thermal sensor has a known accuracy of ±0.02 million W/m². 

• The formulation includes two different sizes of aluminium particles in equal amount. When the propellant burns, these particles oxidise and form two distinct sizes of aluminium oxide droplets, each contributing differently to radiative heat. 

• The aluminium oxide droplets radiates heat as follows:  

Droplet Diameter	Additional Heat from Radiation  (In percentage)
100 nm	+5%
1 µm	+10%
6 µm	+15%
10 µm	+25%

 

The measured heat flux rose to 7.2 million W/m². With a base of 6.0 and a sensor error of ±0.02 million W/m², which two droplet sizes were most likely include in the mix? 

They observe that the heat flux without aluminium, is 6.0 million W/m². 

During testing, when aluminium is added, the recorded surface heat flux increases to 6.6 million W/m². 

Their lab notes indicate that aluminium oxide droplets emit additional radiant heat, depending on droplet size: 

Droplet Diameter	Additional Heat from Radiation (In percentage)
100 nm	+5%
1 µm	+10%
6 µm	+20%
10 µm	+25%

 

The engineers observed a rise in heat flux from 6.0 to 6.6 million W/m² after adding aluminium. Since the additional heat varies with droplet size,  which droplet size was most likely present in the aluminium powder?? 

When Ravi clocks out, his mobile automatically sends a signal to his smart car in the parking area. It takes Ravi 5 minutes to walk down to the basement and get into the car. While he’s walking, the car begins its journey to pick him up from the basement, and during this time, it moves to collect him. Once inside, Ravi begins his journey home, which usually takes 30 minutes to cover 10 km.  

However, today’s changes include: 

• Traffic delay: Adds 3 extra minutes to the journey 

• Petrol detour: The car needs fuel, which adds 6 more minutes 

Additional Tasks in the Smart Home: 

• AC: Starts cooling while Ravi is on the way. The current room temperature is 38°C, and he wants it to be 22°C by the time he arrives. The AC reduces the temperature by 1°C every 2 minutes. 

• Coffee Machine: Should finish brewing just as Ravi arrives. Brewing takes 7 minutes. 

• Oven: Heats food and takes 10 minutes to complete. 

Based on the scenario, identify the correct timestamp and determine which devices should be ON and which should be OFF. 

When Ravi clocks out, his mobile automatically sends a signal to his smart car in the parking area. It takes Ravi 5 minutes to walk to the basement, during which the car also moves to pick him up. At the same time, his smart home starts preparing for his arrival. 

To ensure the room is comfortable when he gets home, the Air Conditioner starts cooling while Ravi is still on the way. The AC reduces the temperature by 1°C every 2 minutes. The room is currently 38°C, and Ravi prefers it to be 22°C on arrival. 

Ravi also enjoys a freshly brewed coffee every evening. The coffee machine is set to begin brewing at the right moment so that it finishes exactly when Ravi reaches home. Brewing a cup takes 7 minutes.  

The drive home takes 30 minutes, covering a distance of 10 km. 

 

Based on the scenario, identify the correct timestamp and determine which devices should be ON and which should be OFF.