Understanding Forces and Energy in Space Exploration

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Homework Help Overview

The discussion revolves around physics concepts related to forces and energy, particularly in the context of space exploration. The original poster is working through problems involving the calculation of force on a rocket, kinetic energy of an astronaut, and the effects of gravity on jumping from heights on the moon versus Earth.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to apply Newton's second law to calculate force and questions the validity of their kinetic energy calculation. They also seek to understand the relationship between gravitational field strength, weight, and acceleration in the context of jumping on different celestial bodies. Additionally, they inquire about the benefits of underwater training for astronauts.

Discussion Status

Participants are engaging with the original poster's questions, offering insights and raising further inquiries about the conditions affecting the rocket's force calculation and the astronaut's jumping scenario. There is a suggestion that the problem may involve considerations of gravitational forces and acceleration, indicating a productive exploration of the topic.

Contextual Notes

The original poster mentions specific values and conditions, such as the rocket's mass and acceleration, the astronaut's drop height, and the context of training underwater. However, there is an indication that some information may be missing or that assumptions about the scenarios need to be clarified.

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Hi I'm doing a practice test paper in preparation for my exam. I've calculated the acceleration of a rocket to be 5m/s². It now says that the average mass of the rocket is 1000kg and asks to calculate the force on the rocket. I assumed that the formula to use would be F=ma so I calculated the force to be 5000N from 1000 x 5 although this was marked wrong. Could anyone please explain where I went wrong?

Then there is a question on an astronaut. He jumps off a rock on the moon and drops 1.5m. His speed is 2.2m/s as he hits the ground. Calculate the kinetic energy of the astronaut as he hits the ground. I used the formula K.E. = 1/2 x mass x speed² to get 1/2 x 150 x 2.2² = 363J. I was wondering if anyone could confirm whether that is right as I have a suspicion it isn't considering they bothered to mention the distance he drops in the question.

Then I have to explain why astronauts can jump down from a height of 1.5m safely on the moon but not safely on earth. I have to make reference to weight, acceleration and energy. So far I've said that on the moon the astronauts weight will be less as the gravitational field strength will be less. Also the astronaut will have less gravitational potential energy as the gravitational field strength is less. Is there a scientific way that I can tie in acceleration in relation to the gravitational field strength?

Finally there is a question asking why it is a good idea for astronauts to do training under water for their work on the moon as opposed to just on the ground on earth. I have forgot the technical words but I'm assuming it is to do with the drag in the water making them move slower :confused:

Any help would be greatly appreciated. Thanks in advance.
 
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No. 1 - are you told how long the rocket travels for? And what about the gravitational force on the rocket?

No. 3 - the acceleration and g and equal I think.

No. 4 - underwater is weightlessness simulation, no effects of gravity, can move in 3 dimensions etc.

-NewScientist
 
Thanks for the reply. Referring to No. 1 I am told that the rock travels in space. It accelerates from a velocity of 100m/s to 700m/s. This takes 120 seconds.
 
Well, it may be a trick question does it ask for the force after acceleration? For if it does the answer is 0 as the rocket will be at a steady speed and so will have acceleration of 0 and therefore the forces are balanced or 0. If they are balanced the net force is 0

-NewScientist
 
EDIT: nevermind :P
 

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