How to Verify Answers for Newton's 3rd Law Problems

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In summary, the conversation discusses various scenarios involving a rocket and its mass, weight, acceleration, and force. The initial mass of the rocket is 25000kg and its weight is 250,000N. The force on the rocket's fuel is calculated to be 562,500N. The net force on the rocket is 25,000N with an acceleration of 10m/s^2. The rocket's speed after 2 seconds is 20m/s. In orbit, the rocket's weight is still 25,000N. An astronaut applies a force of 750N to the rocket, resulting in an acceleration of 10.3 m/s^2. The acceleration of the astronaut, who forgot to tether
  • #1
iuhoosierz
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Could someone please check my work and verify if I am correct? I am not confident about any of my answers except #1. Thank you very much for your time.

1. The initial mass of a giant rocket is 25000kg. What is the weight of the rocket?
Answer: 250,000 N

2. Assume 90% of the mass of the rocket is fuel and is spewed out nearly instantaneously. If the fuel for the rocket travels downward at a velocity of 50 m/s after being accelerated for 2 seconds then what is the force on the rocket's fuel? Ignore gravity on this one.
Answer: A=change in velocity/T so a=25 m/s^2. Then I did F=MA so F=22,500kg*25m/s = 562,500 Is this correct?

3. A.What is the net force on the rocket (remember gravity)?
Answer: F=MA so 2500kg*10m/s= 25,000N I am really iffy about this one

B. What is the acceleration of the rocket?
Answer: A=f/m so a=25,000N/2500kg= 10m/s^2 ?

C. After 2 seconds how fast will the rocket be traveling?
Answer: V=at so V=10m/s^2 * 2s= 20m/s ?

4. Somehow we get the rocket into orbit around the earth.
A. What is the weight of the rocket in orbit (mass = 2500 kg now)?
Answer: F=MA so F=2500kg*10m/s= 25,000N. I wasn't sure what the acceleration would be for this one.

B. If an astronaut applies a force of 750N to the rocket then what will the acceleration of the rocket be?
Answer: A=F/M so A=25,750N??/2500 kg = 10.3 m/s^2 ?

C. The astronaut forgot to tether himself! What will the acceleration of the astronaut be (mass of astronaut is 100N)?
Answer: A=F/M so A= 750N/100N= 7.5 m/s^2

Again thanks for your time. I really need some help with this
 
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  • #2
All correct.
 
  • #3
Thanks for the quick response.

Anyone else care to verify that I am correct?
 

Related to How to Verify Answers for Newton's 3rd Law Problems

What is Newton's 3rd law?

Newton's 3rd law, also known as the Law of Action and Reaction, states that for every action, there is an equal and opposite reaction. This means that when an object exerts a force on another object, the second object exerts an equal and opposite force back on the first object.

How does Newton's 3rd law apply to everyday life?

Newton's 3rd law can be observed in many everyday situations, such as when you walk or run - your feet push against the ground, and the ground pushes back with an equal force, propelling you forward. It also explains how rockets are able to launch into space, as the force of the rocket's engines pushing down against the ground causes an equal and opposite force that propels the rocket upwards.

Can Newton's 3rd law be violated?

No, Newton's 3rd law is a fundamental principle of physics and cannot be violated. Every action will always have an equal and opposite reaction.

How does Newton's 3rd law relate to forces?

Newton's 3rd law is directly related to forces, as it states that forces always come in pairs and are equal in magnitude but opposite in direction. This means that whenever one object exerts a force on another object, the second object exerts an equal and opposite force back.

What is the significance of Newton's 3rd law?

Newton's 3rd law is significant because it helps us understand the interactions between objects and how forces work. It is essential in many areas of physics, such as mechanics and astronomy, and is the basis for many technological advancements, such as rocket propulsion.

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