Une roue comportant un rayon tourne avec une fréquence f . cette roue est éclairées à l'aide d'un stroboscope . La fréquence fe des éclairs est réglable 1- Pour quelles fréquences des éclaires observe-t-on une roue immobile avec un seul rayon ?
2- La plus grande fréquence des éclairs pour laquelle on observe une roue immobile avec un rayon est fe= 40 HZ . Déterminer la fréquence de la roue et sa votesse de rotationen trs/min .
3- Indiquer ce qu'on observe dans les deux cas suivants : fe=120 HZ ; fe=10HZ

Three archers each fire four arrows at a target. joe’s four arrows hit at points 10 cm above, 10 cm below, 10 cm to the left, and 10 cm to the right of the center of the target. all four of moe’s arrows hit within 1 cm of a point 20 cm from the center, and flo’s four arrows hit within 1 cm of the center. the contest judge says that one of the archers is precise but not accurate, another archer is accurate but not precise, and the third archer is both accurate and precise. which description applies to which archer? explain

The lights used by mark watley (played by matt damon) during the film the martian seem to be metal halide lamps. metal halide lamps are filled with vaporized mercury and metal-halogen compounds. when an electric current is passed through the lamp, the tube begins to glow a bright white/blue color. if you were to pass this light through a prism to separate the individual light frequencies, you would see a rainbow just as you would if using natural sunlight because of the complexity of the metal halide gas and the vast amount of possible electron transitions. (the study of light in this way is known as spectroscopy and allows astronomers to know exactly what atoms compose distant stars, simply by looking at the light they emit. the spectral lines an atom produces uniquely identifies that atom just like a fingerprint uniquely identifies a person. the momentum equation and energy equation that we have used above can be combined to give the following equation: c = e p where again p is the phonon momentum, e is the photon energy and c is the speed of light. when you divide the photon energy found in #6 by the photon momentum found in #4, do you get the speed of light? (if not, check your work for questions #4 through #6). yes no

Dao makes a table to identify the variables used in the equations for centripetal acceleration. what quantities belong in cells x and y?