Why? It seems perfectly sensible to me. Maybe you are confused by the fact that with an internal combustion engine, power does not come on till you are at a sufficiently high engine speed. Try this: With a gear chosen so that you are near maximum power output for your car at so 50km/h, hit the throttle suddenly and note how hard it presses you back into your seat. That's a measure of acceleration. Now do the same at 100km/h. You will notice considerably less force pressing you into your seat at the higher speed.Originally posted by kishtik
Think a car speeding up from 0 to 30. It cannot have the same acceleration when it continues to 60 km/h. It seems nonsense.
The torque delivered by the engine is a function of R.P.M. As the RPM increases there is a power peak range where there is a maximum power being delivered by the engine. As the rpm increases past that point the power starts to drop off.Originally posted by kishtik
I cannot imagine P=F v cosa alhough I know its mathematical derivation.
Think a car speeding up from 0 to 30. It cannot have the same acceleration when it continues to 60 km/h. It seems nonsense.
Can you help me understand this better?
Any help is appreciated.
LOL. Still, that doesn't stop some of us from trying!Originally posted by pallidin
If 30 to 60 mph acceleration only required the same energy as 0 to 30 mph, than space travel would be far, far easier, and anyone could do it in their own backyard.
Not really. For low speed travel, a=f/m. A rocket actually accelerates FASTER the faster it gets because its mass is decreasing.Originally posted by pallidin
Just a comment, but I think of it this way:
If 30 to 60 mph acceleration only required the same energy as 0 to 30 mph, than space travel would be far, far easier, and anyone could do it in their own backyard.
In which case one uses dp/dt = d(mv)/dt = m*dv/dt + v*dm/dtOriginally posted by russ_watters
Not really. For low speed travel, a=f/m. A rocket actually accelerates FASTER the faster it gets because its mass is decreasing.