Thrust of a rocket at lift-off

In summary, the conversation is discussing a question about an ancient A lvl problem and finding the thrust of a rocket prior to lift-off. The conversation suggests using dimensional analysis to find the thrust, and also mentions that a force is a change of momentum. The reason for the interval between ignition and lift-off is not explicitly stated.
  • #1
Kodomut
1
0
Need help with an ancient A lvl question. Just can't visualise the whole process even though I drew out the diagram

A space research Rocket stands vertically on its launching-pad. Prior to ignition, gas is ejected from the rocker at a speed of 2.5x10^3 ms^-1 relative to the rocket, and fuel is consumed at a constand rate of 7.4kgs^-1. Find the thrust of the rocket and hence explain why there is an interval between ignition and lift-off


g = 10ms-2


I have totally no idea how to find the thrust. =(
 
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  • #2
there's not much one can do with two numbers. Try some dimensional analysis to see if it fits.

But regardless...you can already have an idea about the second question. Take a guess.
 
  • #3
BTW: a force is a change of momentum (the derivative)
 

1. What is the thrust of a rocket at lift-off?

The thrust of a rocket at lift-off is the force that propels the rocket upwards. It is generated by the rocket's engines and is measured in units of force, such as newtons or pounds.

2. How is the thrust of a rocket at lift-off calculated?

The thrust of a rocket at lift-off is calculated by multiplying the mass of the propellant being expelled by the velocity at which it is expelled. This is known as Newton's Second Law of Motion: F = ma, where F is the force (thrust), m is the mass, and a is the acceleration.

3. What factors affect the thrust of a rocket at lift-off?

The thrust of a rocket at lift-off is affected by several factors, including the type and design of the rocket's engines, the amount and type of propellant being used, and external forces such as air resistance. The altitude and atmospheric conditions at the launch site can also impact the thrust of a rocket.

4. What is the relationship between thrust and lift-off speed?

The thrust of a rocket at lift-off is directly related to its lift-off speed. As the thrust increases, so does the lift-off speed. The thrust must be greater than the weight of the rocket for it to lift off the ground and begin its ascent into space.

5. How does the thrust of a rocket at lift-off change during flight?

The thrust of a rocket at lift-off will decrease as the rocket ascends and expends its propellant. This is because the weight of the remaining propellant decreases, resulting in a lower thrust-to-weight ratio. The rocket's engines may also be throttled down or shut off completely once the desired altitude and speed are reached.

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