/g/ can't solve this. Can Veeky Forums?
An old car has to travel a 2-mile route, uphill and down. Because it is so old, the car can climb the first mile - the ascent - no faster than an average speed of 15mi/h. How fast does the car have to travel the second mile - on the descent it can go faster, of course - in order to achieve an average speed of 30 mi/h for the trip.
it has to teleport back down the hill because in travelling up the hill at 15 miles an hour it has already used up all the time it has available to make the total journey up and down the hill at an average speed of 30 miles an hour.
a 2 d journey done with an average speed of 30 miles per hour takes 2 d / 30 hours which is equal to d / 15 hours, which is how long it takes to go up the hill of length D travelling on average at 15 miles per hour
try v next time, brainlet
Average speed = (ascent speed + descent speed) / 2
30 = (15 + X) / 2
X = 45
Sit down kid
-1/12 mph
I'm confused
brainlet detected
15mi/h for 1 mile is 4 minutes
45mi/h for 1 mile is 1,33... minutes
total
45mi/h for 25% of the time
15mi/h for 75% of the time
0.75*15+0.25*45=22.5mi/h avg is what your answer gets
how much does the car weight?
the answer is infinity miles per hour
885 mph average downhill leads to an average of 29.5 mph
Since speedometers don't show decimal numbers this will be rounded up to 30 mph
Lol!
60mph easy
what is the speed limit
Oh look, it's the guy that would get hired at Google
...
(15mph*1)/2
Then you just plug in 9.8m/s^2 to account for gravity and multiply by pi
The answer is 78mph
Take that /g/
Speed is a weighted average, dumbass, if you spend 90% of your time going 2 mph, and then 10% of your time going 50 mph, then your average speed isn't (50 + 2)/2 = 26 mph. Your average is going to be 0.9*2 + 0.1*50 = 2.3 mph. In terms of the problem, because the car can go no faster than 15 mph on the 1 mile ascent, we know that the car will take 0.0666... hours or more to reach the turn point. After the turn point, the car drives down the 1 mile stretch at some speed x mph such that the average speed of the trip is 30 mph. To compute this, we calculate the time associated with the descent, which is 1/x hours. Now, we need to convert this into a fraction of the total time, where the other stretch of time is 1/y (where y≤15 mph), which gives us (1/x)/((1/x)+(1/y)) for 1/x and (1/y)/((1/x)+(1/y)) for 1/y So the equation we have to solve is [(1/x)/((1/x)+(1/y))]*x mph + [(1/y)/((1/x)+(1/y))]*y mph = 30 mph, y≤15 mph. Simplifying, we get 2/((1/x)+(1/y)) = 30 mph, 1/15 = (1/x)+(1/y), but y≤15, so (1/y)≥1/15, and (1/y)+(1/x)≥1/15 + (1/x)>1/15, hence (1/y)+(1/x)>1/15, a contradiction. Therefore, there is no value x that satisfies this.
but you dint take the curvature of the earth into account?? or if the driver really needed a poo???
this is easy as fug
If the car went 15 miles in one hour it already used up all its time. It would have to instantaneously be at 30 miles to have gone 30 miles in one hour. Parameterizing this with distance doesn't change the fact that you are already out of time.
This is just like saying If John runs twice as fast as Jane, after one lap of a two lap race, how much faster does Jane have to run than John to win? John has already won.
What makes you think going one mile at 15mph takes an hour?
Didn't account for coriolis effect or the force exerted on the car by the skyscraper sized electromagnet at the top of the hill.
1 mile at 15mph uses up 4 minutes, meaning the car would have to clear the next mile at a speed equivalent to 29 miles in 28 minutes, ergo, just over 60mph.
explain this faggots.
negro please i am failing physics
45 mph, I'm sure /g/ had no problem answering this.
(15 + x) / 2 = 30
x = 45 mph
We are looking find the an average speed of thirty miles per hour. Average is found by dividing the sum of all component speeds traveled by the number of various speeds traveled. So 30= (15 + x ) / 2, because the desired average speed of 30mph is a result of the ascent average speed of 15 plus and unknown average that sum divided by two (the number of component average speeds).
30 = (15 + X) / 2
30 = 15/2 + X/2
45/2=X/2
X= 45/2 * 2/1
X= 90/2
X=45
Where did you get that?
brainlets detected.
See Veeky Forums is dumber than I thought.
How is the correct answer found?
If the first half is traveled at 15 mph then wouldn't the total journeys average speed be determined by the first half plus the second half divided by two?
fuck off, the problem is bait and doesn't have an answer, go back to
kek 9/10 b8
To travel a distance of 2 miles at an average speed of 30 mph would take (2/30)*60= 4 minutes
If you travel for 1 mile at 15 mph you spend (1/15)*60 = 4 minutes
So, it is pretty obvious my kohai, the speed of light itself.