why do frictional forces reduce the efficiency of machines?
2006-10-23 08:23:37 · 3 answers · asked by Anonymous in Science & Mathematics ➔ Physics
Remember that friction is caused by small imperfections in surfaces or intermolecular surface interactions. You can picture these as small "bumps" in two surfaces interacting, with some bumps falling into others and needed to be pushed out of them.
All of this movement causes molecules within the two mating materials to agitate and vibrate more than they did before. We experience this additional vibration as heat. If we touch a surface that has been sufficiently agitated, some of that agitation is transfered to molecules in our skin and our nerves feel an additional stimulation that we experience as warmth. Enough additional movement is dangerous for the structures in our skin, which is why we have a notion of something being "too hot" to touch -- our body reaches a threshold where so much stimulation from our nerves triggers a reflex that pulls us away from the source of the heat.
Now, all of this new movement in surfaces being rubbed together has to be powered by something. It comes from the movement of the large object as a whole. The large object gradually slows down as the energy of its forward movement gets turned into the energy in the agitation of molecules near its surface. In other words, the kinetic energy gets turned into heat energy.
Thus, frictional forces cause kinetic energy, the energy of movement, to leak away into heat. That means that in order to keep something moving, we must add more energy than we would nominally expect. This additional energy makes the machine less efficient. Plus, the build up of heat can cause damage to the machine (just like it can damage our skin) so we often have to add other materials to lubricate the surfaces. This not only reduces friction, but it helps transport the heat away from the surfaces quickly, letting them cool to a safe level.
2006-10-23 08:57:02 · answer #1 · answered by Ted 4 · 0⤊ 0⤋
JiHyun is correct. Also, I'd like to add that friction is a resistant force, that is it will cause a resistance to what ever operation the machine is doing, which is why more energy will be required.
2006-10-23 15:30:27 · answer #2 · answered by ohmneo 3 · 0⤊ 0⤋
Because frictional forces create losses of energy due to heat. Because you are losing energy, the output energy is less.
2006-10-23 15:28:00 · answer #3 · answered by FoodLOVER 2 · 0⤊ 0⤋