Calculating Resultant Force and Energy in Physics Homework Problems

[zeldaspurpose]

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

 

[haruspex]

1000N+1800N - 500N = 2300N

It says "a rocket of 1000N". What do you think that means?

Edit: please use a separate thread per problem.

 

[zeldaspurpose]

I meant force! And sorry, I'll do that next time.

 

[haruspex]

I meant force! And sorry, I'll do that next time.

No, surely the 1800N is the thrust. Isn't the 1000N the weight?

 

[zeldaspurpose]

I checked the question in my book and yes, it is weight. I am really sorry.

 

[haruspex]

I checked the question in my book and yes, it is weight. I am really sorry.

So how does that change your equation?

 

[zeldaspurpose]

The equation e= mgh is for the second question. The answer to the first question is 300N, but I am not understanding why.

 

[haruspex]

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

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

 

[zeldaspurpose]

I looked into it and I understood now, thanks for the help.

 

[Kaura]

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?