Question about the upthrust of a rocket

In summary, the Saturn V rocket used in the Apollo space missions had a mass of 3.0 x 10^6 kg, an exhaust velocity of 1.1 x 10^4 m/s, and an initial rate of fuel consumption of 3.0 x 10^3 kg/s. The force produced at lift-off was 33 MN, and the resultant force acting on the rocket at lift-off was 3.6 MN. The equation Ft = mv/t was used to calculate these values, with the help of an upthrust value of 9.81 m/s^2.
  • #1
ThatOneMidget
6
1

Homework Statement



The Saturn V rocket which launched the Apollo space missions had the following specifications: mass at lift-off = 3.0 x 10^6 kg velocity of exhaust gases = 1.0 x 10^4 m/s initial rate of fuel consumption at lift-off = 3.0 x 10^3 kg/s 1.(a) Calculate: (i) the force (thrust) produced at lift-off (ii) the resultant force acting on the rocket at lift-off

Homework Equations



Ft = mv

The Attempt at a Solution



i got the force exerted by the exhaust gases by rearranging the equation to F = mv/t. Upthrust was 33MN. But then i have no clue how to figure the second part out, the solution page says it is 3.6MN, i keep getting 3MN, any help would be greatly appreciated!
 
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  • #2
I don't see how you got the thrust value of 33 MN from the given information, notr how they arrived at 3.6 MN for the resultant force. Check the given value for the exhaust velocity: Was it perhaps a bit higher than 1.0 x 104 m/s?
 
  • #3
My bad, it's 1.1*10^4 m/s
 
  • #4
ThatOneMidget said:
My bad, it's 1.1*10^4 m/s
Does that resolve your issues?
 
  • #5
I'm still getting 3MN for the net force, and 33MN for the upthrust
 
  • #6
It seems like the book used 9.81 as a value for g although it stated to use 10 = g, anyways I've got it :D
 
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Likes gneill

FAQ: Question about the upthrust of a rocket

What is upthrust in relation to rockets?

Upthrust, also known as buoyancy, is the force that pushes an object upwards when it is submerged in a fluid. In the case of rockets, it is the force that counteracts the weight of the rocket, allowing it to lift off and fly through the air.

How does the shape of a rocket affect its upthrust?

The shape of a rocket can greatly impact its upthrust. A streamlined shape, with a pointed nose cone and gradually tapering body, reduces air resistance and allows for more efficient movement through the air. This, in turn, affects the amount of upthrust generated by the rocket.

What factors affect the upthrust of a rocket?

Several factors can influence the upthrust of a rocket, including its shape, size, weight, and the density of the fluid it is moving through. Additionally, the speed and direction of the rocket can also impact the amount of upthrust generated.

How is upthrust calculated in rocket design?

In rocket design, upthrust is typically calculated using the Archimedes' principle, which states that the buoyant force on an object is equal to the weight of the fluid it displaces. This allows engineers to determine the necessary size and shape of the rocket to generate enough upthrust to lift off and maneuver through the air.

Can upthrust be manipulated for better rocket performance?

Yes, upthrust can be manipulated to improve rocket performance. This can be achieved through various design elements, such as adding fins to increase surface area and reduce air resistance, or adjusting the weight and balance of the rocket to optimize the amount of upthrust generated.

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