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Friday, 29 April 2011

n.15 - motociclista

A motorist drives North for 35 min at 85 km/hr and then stops for 15 minutes. He then continues North, traveling 130 km in 2 hr. What is the total displacement? What is the average velocity?

From A to B : 35 min at 85 km/hr
From B to B : 15 min at rest
From B to C : 2 hr on a distance of 130 km

D = Displacemnet A -- > C = (130+ 35/60 hr x 85 km/hr) = 179 km
Average velocity = D/t = 179 km / (35/60+15/60+2) hr = 63.2 km/hr
In the average velocity, we have the tital time, including also 15/60 hr,  the time spent at rest.