# Recent content by Emanresu

1. ### Man versus Iron Weight

Duh ! It seems so obvious now ! Thanks, E.
2. ### Man versus Iron Weight

http://www2.uah.es/jmc/ai14.pdf On page 2 of the above pdf there is an example in a box with title 'Acceleration' which states that there is a difference between a man pulling on a rope with 600N force and an iron weight of 60Kg (g = 10) tied to the rope. The difference being that once the...
3. ### Thickness of bulb filament affect brightness?

I am interested to know why that is ... E.
4. ### I was changing a light pendant today

and considered doing this with just the switch turned off. After turning off the switch I checked the voltage with a meter in A/C mode. It was 140V which I thought a tad high. When I turned the switch on the reading was 230V as expected (in the UK). So I turned off the lighting circuit at the...
5. ### Power from F time v

Suppose you have a frictionless and perfectly balanced conveyor belt going into space (and back). The belt is driven by a motor on earth. Suppose you want to send a person who weighs 100kg into space and you boost them onto the conveyor belt at 1m/s with the conveyor belt running at 1m/s (the...
6. ### Why kinetic energy is proportional to velocity squared

Hi Jeff, I didn't give your posts due attention the first time I read them. They are very insightful (no math :smile:). Thank you. E.
7. ### Why kinetic energy is proportional to velocity squared

So then the rate at which the rocket gains kinetic energy DECREASES ? But the rocket's acceleration INCREASES ? And the explanation for both of these is that the rocket's mass is DECREASING ? E.
8. ### Why kinetic energy is proportional to velocity squared

No. I quoted what you gave for the EXHAUST GAS ONLY. Please re-read my question. I know my questions APPEAR stupid to you because you know the subject inside out, but I genuinely am just trying to understand this one bit at a time. E.
9. ### Why kinetic energy is proportional to velocity squared

Okay. I've worked through your math and am happy enough with it. In order to get some insight I started plugging in numbers. It appears that the faster the rocket is going the more energy is transferred to the exhaust gas \frac 1 2 \Delta m v_r^2 + \Delta m v_r\cdot v_e + \frac 1 2...
10. ### Why kinetic energy is proportional to velocity squared

Thanks again. I'm happy with the principle now, although I'm going to have a go at working through DH's rocket math just out of interest. E.
11. ### Why kinetic energy is proportional to velocity squared

Originally I thought that constant rate of energy supply would provide constant force so I was confused as to why energy out (KE) was proportional to v^2. Then as result of answers given here I was persuaded that a constant force would not result which explained why KE was not proportional to v...
12. ### Why kinetic energy is proportional to velocity squared

You are a bit over my head here, but when you say 'Since the mass is constant, the change in vehicle velocity is also proportional to energy transferred to the vehicle', is there a constant force on the vehicle ? E.
13. ### Why kinetic energy is proportional to velocity squared

No problem. What you explained earlier made sense. But I am confused again as I didn't follow DH's argument. If now 'Constant rate of fuel production does produce a constant force' I am back to square one. Can you explain DH's argument for me ? E.
14. ### Why kinetic energy is proportional to velocity squared

Thanks very much, I'm starting to get my head round it now.
15. ### Why kinetic energy is proportional to velocity squared

Thank you for your answer. I accept what you say as a fact. So my confusion is to do with why a constant rate of fuel consumption does not produce a constant force. Can you explain this please ? E.