Simple physics question ?

Question

A person takes a trip, driving with a constant speed of 96.5 km/h except for a 20.0 min rest stop. If the person's average speed is 63.4 km/h, how much time is spent on the trip and how far does the person travel?

Do you do 96.5/3600 km/s + x*20/60 = 63.4

Answer 1

Quite an idealistic problem :)

A constant speed of travel to a dead stop and then back to a constant speed !!

Anyway, make an equation for the total distance traveled where x = the total travel time.  You don't necessarily have to convert the km/hr to km/min because it will just fall out since it is a ratio.

96.5 km/hr * (x-20) + 0 km/hr * (20 min) = 63.4x

Simplify:

33.1x=1930

x = 58.31 min. total time

x - 20 = 38.31 min. driving time

total distance traveled = (63.4 km/hr * 58.31 min)/60 min/hr

= 61.61 km

Answer 2

It took me a while to understand the question.

The person traveled at a constant speed of 96.5 but after a 20 minute rest stop it ended up being an average speed of 63.4.  So the question is "How far did they go and how long did they drive?"

I took 96.5 X 2/3 ( the 2/3 because that's how much of an hour that they were driving ) = 64.333.  So they were driving for about 59 minutes and went 64km.

Don't ask me the right way to do this question though.  ;-)

I had to look over the answers that you got.  JS did it right.  I was close though.  hehehe

Answer 3

nope

try this:

((96.5)(time) + 0(20 mins))/(time + 20 mins) = 63.4

then cross multiply, making this:

((96.5time + 0) =  63.4time + 1268

then transpose like terms: remove the zero

96.5time - 63.4time = 1268

then this:

33.1time = 1268

divide it to obtain time:

time = 38.30 minutes

after getting the time, get the velocity by multiplying the velocity to the time:

convert first the time to hour 0.6383 hours of travel.

then multiply it:

distance = velocity * time

distance = 96.5*0.6383

distance = 61.6 kilometers

therefore,  they traveled 61 kilometers for 38 minutes. i hope that makes things clear. Email me for oter questions. if you want, substitute the value of time. i just want you guys to understand that you got a big misconception on this problem. you forgot that "ThE total time" is needed to get te average and then the velocity's variable is its time. check out the formula on my resources. Thanks :D. i hope all of you got it now right ^_____^