- #1

digalumps

- 12

- 1

- Homework Statement
- Question about kinetic energy

- Relevant Equations
- KE=1/2 mv squared

I have a problem regarding Kinetic Energy which as we know is 1/2 m v squared.

Say I have a 1kg mass moving at 10 meters/second. I have a 1 Newton rocket which I attach to the back and it burns for 1 second accelerating the mass by 1 m/sec/sec to 11 m/sec. The KE originally was 50 joules and it has now increased to 60.5 joules.

Now say I have the same mass moving at 1000 m/sec and I do the same thing. It accelerates to 1001 m/sec. The KE goes from originally 1000 squared to 1001 squared ie an increase of 2001 joules - a much bigger increase.

It is the same rocket with the same amount of gunpowder so where has the 'extra' energy come from?

I know in the second case the distance moved in the 1 second of rocket burning is larger, and work=force x distance moved so equation-wise I can see but not intuitively as it is the same rocket with the same amount of input energy.

Say I have a 1kg mass moving at 10 meters/second. I have a 1 Newton rocket which I attach to the back and it burns for 1 second accelerating the mass by 1 m/sec/sec to 11 m/sec. The KE originally was 50 joules and it has now increased to 60.5 joules.

Now say I have the same mass moving at 1000 m/sec and I do the same thing. It accelerates to 1001 m/sec. The KE goes from originally 1000 squared to 1001 squared ie an increase of 2001 joules - a much bigger increase.

It is the same rocket with the same amount of gunpowder so where has the 'extra' energy come from?

I know in the second case the distance moved in the 1 second of rocket burning is larger, and work=force x distance moved so equation-wise I can see but not intuitively as it is the same rocket with the same amount of input energy.