La « lampe torche » que possède Sofia n'éclaire plus ; le boîtier contient trois piles, chacunes des tensions nominales est égale à 1,5 V; elles sont branchées en série pour alimenter l'ampoule à
D. E.L. avec une tension nominale de 4,5 V.
Pour déterminer l'origine de la panne, Sofia dispose d'un multimètre dont les calibres sont :
1 000 V; 200 V; 20 V; 2 V; 200 mV.
1 - Sofia effectue le branchement pour mesurer la tension d'une pile ; elle sélectionne d'abord
calibre 1 000 V du multimètre et l'écran affiche la valeur : 001
Commente ce résultat et explique pourquoi Sofia doit adapter le calibre en fonction de la
mesure.

Answertraveling around a circular trackexplanation"traveling around a circular track" is the best answer as you could be traveling around a circular track at a constant speed. your velocity would therefore have the same magnitude but will always be constantly direction. since acceleration is the rate of change of velocity, the rate of change will only involve the direction of velocity and not the magnitude.wrong choices: "an object at rest" does not accelerate at all"increasing speed while traveling around a curve" means that the acceleration will not be constant due to only change in direction; it will be constant due to both magnitude and direction"an object in free fall" does not necessarily change direction 

Distance covered = speed x timethe distance traveled going against the stream = distance traveled with the stream.therefore it is the speed and the time that are the variables.as he travels the same distance both ways, speed x time is the same for each way.going upstream his speed is 4 kph; going downstream his speed is 6 kph.therefore we have two simultaneous equations: time upstream x 4 = time downstream x 6time upstream + time downstream = 60 minutestherefore we have the equation: time upstream = 6/10 hour, time downstream therefore = 4/10 hour.distance traveled at 4km/hr in 6/10 hour = 24/10 = 2.4km.check: distance traveled at 6km/hr in 4/10 hour = 24/10 = 2.4km.

Despite their crazy structure, human bones are surprisingly good!