Two cars are driving toward each other on a straight and level road in Alaska. The BMW is traveling at 104.8 km/h north and the VW is traveling at 40 km/h south, both velocities measured relative to the road. At a certain instant, the distance between the cars is 11.0 km. Approximately how long will it take from that instant for the two cars to meet? [Hint: Consider a reference frame in which one of the cars is at rest.]
2007-06-12 16:18:41 · 6 answers · asked by terra_flare_aqua_ciel 1 in Science & Mathematics ➔ Physics
because the two cars travel to each other, when the meet, their distance will add to 11km
x = vt
distance of BMW is x = 104.8t
distance of VW is x = 40t
104.8t + 40t = 11
144.8t = 11
t = .079668508 hrs or about 4.6 minutes
2007-06-12 16:30:59 · answer #1 · answered by 7 · 1⤊ 0⤋
Take the reference point of the BMW. In this car, it looks as if the VW is traveling at
v = 104.8 + 40 = 144.8 km/h
toward it. Since we know the distance between the two cars, we can use the famous formula x = v t and get
t = x / v = 11 / 144.8 = 0.07597 hr = 4.56 min
2007-06-12 16:32:19 · answer #2 · answered by Boozer 4 · 0⤊ 1⤋
In order to solve this you need to set the equation for the distant car 1 travels to the distance car 2 travels. This would look like (30)s = (20)s + 20(5), you need to have the 20(5) since that is the head start car 1 had before car 2 got to the intersection.
2016-05-18 22:56:45 · answer #3 · answered by ? 3 · 0⤊ 0⤋
Maybe, 11/ (104.8+40)? = 0.076hours or 4..56 minutes
If they were both going the same direction, and the BMW was overtaking the VW, it would be 11/(104.8-40) = 10.18minutes, but that is a different question.
2007-06-12 16:34:28 · answer #4 · answered by tinkertailorcandlestickmaker 7 · 0⤊ 2⤋
To answer this question you want to calculate the average speed of the two cars and then divide the 11.0 km by the average speed to get the time to 'collision'.
(104.8 + 40)/2 = 72.4 km/h
11.0 km/72.4 km/h = .1519 hours (this is approximately 9 minutes)
Somebody is correct - I forgot to allow for the distance to impact by dividing 11 km by 2!
2007-06-12 16:31:06 · answer #5 · answered by Doctor J 7 · 0⤊ 2⤋
BMW: speed = 104.8km/h, time = t
VW: speed = 40km/h, time = t
Distance = speed x time
DistanceBMW + DistanceVW = 11
104.8t + 40t = 11
144.8t = 11
t = 0.076 hours
t = 4.558 minutes
2007-06-12 16:40:14 · answer #6 · answered by Kemmy 6 · 0⤊ 1⤋