Calculating Resultant Force and Energy in Physics Homework Problems

  • #1
zeldaspurpose
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Homework Statement


A rocket of force 1000N is propelled upwards by a thrust of 1800N. The air resistance is 500N.

a) Work out the resultant force on the rocket.

A bungee jumper of mass 60kg jumps from a bridge tied to an elastic rope which becomes taut after he falls 10m. Consider the jumper when he has fallen another 10m and is traveling at 15 m/s.

A) Work out how much energy is stored in the rope. Take g= 10 m/s squared and ignore air resistance.

Homework Equations



E = mgh

The Attempt at a Solution


1)a)
1000N+1800N - 500N = 2300N

2)a)
60*10*10 = 6000J
 
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  • #2
zeldaspurpose said:
1000N+1800N - 500N = 2300N
It says "a rocket of 1000N". What do you think that means?

Edit: please use a separate thread per problem.
 
  • #3
I meant force! And sorry, I'll do that next time.
 
  • #4
zeldaspurpose said:
I meant force! And sorry, I'll do that next time.
No, surely the 1800N is the thrust. Isn't the 1000N the weight?
 
  • #5
I checked the question in my book and yes, it is weight. I am really sorry.
 
  • #6
zeldaspurpose said:
I checked the question in my book and yes, it is weight. I am really sorry.
So how does that change your equation?
 
  • #7
The equation e= mgh is for the second question. The answer to the first question is 300N, but I am not understanding why.
 
  • #8
zeldaspurpose said:
The equation e= mgh is for the second question. The answer to the first question is 300N, but I am not understanding why.
I mean this equation
zeldaspurpose said:
1)a)
1000N+1800N - 500N = 2300N
 
  • #9
I looked into it and I understood now, thanks for the help.
 
  • #10
For the second one if I am not mistaken would one not have to use gravitational potential energy and kinetic energy to find the amount of energy that was transferred to the rope?
 

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