a box is pushed up a ramp with a total effort of 65 newtons .
the efforrt,disregarding friction, is 40 newtons. if the box weighs
280 newtons and if the top of the ramp is 5 meterrs abov the ground.
how long is the ramp.?
how much is the efficency of the ramp?
2007-10-22 13:40:15 · 1 answers · asked by :}smile :} 1 in Science & Mathematics ➔ Mathematics
Please don't use the word "effort" when you mean "force". It confuses the issues.
Let's start with the frictionless case. An ideal (friction free, etc.) machine allows you to trade force for distance, but the total work done remains constant.
Work = force x distance
Raising the box straight up thus requires a total work of:
E = weight of the box x height raised
If we raise the box the same height by pushing it along a ramp, the force needed is lower, the distance greater, and the total energy the same:
E = pushing force x ramp length
To calculate efficiency, we have to take friction into account. We know the potential energy the box has just from being raised the 5 meters. We also know the length of the ramp and the force needed to push the box up the ramp against when friction is present:
total work done = pushing force x ramp length
The efficiency ( from 0 to 1, multiply by 100 to get percent) is:
(energy of the raised box)/(energy required to raise the box)
2007-10-23 18:55:56 · answer #1 · answered by simplicitus 7 · 1⤊ 0⤋