An individual white led (light-emitting diode) has an efficiency of 20% and uses 1.0 w of electric power. a. how many leds must be combined into one light source to give a total of 1.6 w of visible-light output (comparable to the light output of a 40 w incandescent bulb)? b. what total power is necessary to run this led light source?

Aboat that travels with constant speed of 6.10 m/s in still water is to go directly across a river. the current in the river flows at 1.95 m/s. (a) at what angle must the boat be steered?

Consider two less-than-desirable options. in the first you are driving 30 mph and crash head-on into an identical car also going 30 mph. in the second option you are driving 30 mph and crash head-on into a stationary brick wall. in neither case does your car bounce off the thing it hits, and the collision time is the same in both cases. which of these two situations would result in the greatest impact force?

Is the portion of the electromagnetic spectrum that has a frequency just above that of visible light.