How did you get 157? I got something in region of 4-500... Do you have a copy of the question at hand so I can try see how it went?
Well because it is a significantly larger distance from the base of the post, where you take the moment from. It is going to be significantly smaller than the 870N value. Considering a basic ratio, it would be much smaller than 400-500.
The efficiency one, you know the velocity to be 0.4m/s so in 1 second it rises by 0.4mYou can use E=mgΔh to find out the energy (which if also the power) then P=VI (or something like that) and use the two powers to find efficiency
for this one, times velocity by the weight to get power, then times v and i to get imput power and find efficiency. ENERGY IS NOT POWER
for this one, times velocity by the weight to get power, then times v and i to get imput power and find efficiency. ENERGY IS NOT POWER
I'm aware that Energy is not power...
However, if you're calculating the energy transferred across 1 second then that would be the same as the power. I think the mass was 0.05kg and the velocity was 0.4ms^-1
So velocity x weight = v*m*g (your calculation) = 0.4*0.05g
E= mgh, when travels 0.4 m in 1sm E = 0.4*m*g = 0.4*0.05g