A car has to travel 2 miles. It travels the first mile at an average speed of 30 miles an hour. How fast does it have to travel the second mile to have an overall average speed of 60 miles an hour?
199491
You would have to travel the last mile at an infinite velocity to average 60mph over the total 2 miles\n\nV = 1/(2/60 - 1/30) = 1/0 = infinity\n\nEDIT- more descriptive version of the equation\n\nDt/Vt = D1/V1 + D2/V2\nhence\nV2 = D2/(Dt/Vt - D1/V1)
504874
If initial speed is V0 and the speed after a time t second is V,\n\nAcceleration is change in speed per unit time.\n\nAcceleration a = (V - VO) / t.\n\nThe average speed during this time t is \n\nV (average) = (V + V0) / 2.\n\nNote; if any quantity is changing uniformly, the average is found by adding the initial and final value and dividing the sum by 2.\n\nThe average speed can also be determined by dividing the total distance by total time of travel.\n \nV (average) = S / t.\n\nTherefore S/t = (V + V0) / 2.\n\nS = (V + V0)* t / 2.\n\nFrom a = (V - V0) / t we have V = V0 +at.\n \nTherefore S = {V0 +at + VO} * t /2 \n--------------- = {2 V0 t + at t } /2\n\n-------------- S = V0t + 0.5 a tt
514801
Something's wrong with the writeup for the first question.  I'm guessing it should have said THR = RHR + 0.65(MHR-RHR), because otherwise you're gonna get a THR of, like, 10000 beats per minute.\n\nProceeding from that assumption, the THR is RHR + 0.65(MHR-RHR).  You're told that the RHR is 54 bpm.  The MHR is 220 - the age(43), so it's 177.  Therefore the THR is 54 + 0.65(177-54) = 54 + 0.65(123) = 54 + 79.95 = 133.95 bpm.\n\nIn the second question, you didn't provide the "following equations," but think of it this way.  The airplane flew for a total of 15 hours at an average speed of 350 miles per hour.  That means it went 5250 miles.  In the final 7 hours it went 2275 miles.  So in the first 8 hours it had to go 2975 miles.  2975 miles/8 hours = 371.875 mph.  I don't exactly know how to write that in an equation, but now that you understand the reasoning, hopefully you'll be able to recognize the correct equation.  If all else fails, plug the data into each equation and see which one returns 371.875.
167412
well if the train is a mile long and the tunel is a mile long then as soon as it hit the tunnel it would have to travel 2 miles to get the whole train through the whole tunnel so since he travels 60mph then it's a mile a min. therefore he needs to to travel 2 miles so it would take him 2 minutes to get through it.
39489
A would take 22 minutes to get to 15 miles and 32 minutes to get to 20 miles. Unfortunately, there's insufficient information to be precise on B's journey. Did he spin off before the start?.. or at which point en route? Guessing it, I would say A arrived at 15 miles and at the 20 miles point first. NB. I have had to make certain assumptions in your question to arrive at this answer (eg I asumed A slows down to 40mph after 4 miles?)
485899
44.44444 mph.  If the distance of one leg is x miles, then you drove a total of 2x miles in (x/40 + x/50) hours.  Divide the total distance driven by the total time spent driving, and you get 200/9, or 44.444... mph
675173
It does not matter how many seconds your car moves in first gear, after that it should be 60 miles/hour and the feets you do the math by yourself. GOT IT???DUHHH
367643
135 miles / (60 miles / hour)\n\n= 135 miles * (1 hour/60 miles) = 2.25 hours\n\nThe way to work these kinds of problems out is to pay attention to the units.  \n\nRemember that "miles per hour" means that number of miles divided by one hour.  You are given miles and miles per hour, so what operation between "m" and "m/h" yields only time (hours or h) as a result?  The answer is m divided by (m/h).
401110
The distance travel is going to be 1/2 mile.   How far away are you are from the beginining of the first 1/4 mile could vary depending on how straight of a line you traveled and which angle you turned once you stopped but the maxium distance can not be greater than 1/2 mile (perfectly striaght line).  So C and D can not be correct.  A and B can be correct.  Being a perfectly straight road is not very possible then A is correct.  But if this is for your math class then most likely B is what the teacher is looking for.
372851
a) F = ma \nYou're given F = -6070 N (negative because it's in the opposite direction) and m = 2600 so a = -2.33 ms^-2. Then over 1.76s, the change in velocity is (-2.33)(1.76) = -4.10 m/s. Car velocity is then 34.9 - 4.10 = 30.8 m/s.\n\nb) v^2 = u^2 + 2as\nv = final velocity = 30.8 m/s (from above)\nu = initial velocity = 34.9 m/s\na = acceleration = -2.33 ms^2 (from above)\nRearrange to get s = (v^2 - u^2)/2a = 155.61 m\n\nc) v = u + at\nYou want v = 0. So if the force is constant then acceleration is constant at 2.33ms^-2. \nu = initial velocity = 34.9 m/s\nSo rearrange to solve for time: (v-u)/a = t = 14.98 seconds.\n\nHope that helps. And learn your equations!
403179
East bound speed=x, in 5 hours 5x\nWest                     =x+6,             5x+30\n10x+30=240\nx=21 miles per hour.\nEast=21\nwest=27\nVR
239957
He has to drive two miles (one mile up and one mile down) in two minutes.  He already took two minutes to get up the hill, so it is impossible for him to average 60 mph.
368219
I'm going to use minutes instead of hours.\nWe know that on the first trip, D = 120S (D=distance, S=Speed of first trip).\nWe know that one the second trip, D = 90(S+6).\n\nTherefore 120S = 90S + 540, or 30S = 540, and S = 18kph.\nTherefore the distance is 36 kilometers.\nChecking, 24(1.5) for the second trip also = 36.
424042
180 miles per hour to go 400 miles is 2.22 hours or about 2 hours and 18 minutes. Stopping for 2 minutes would make the total time 2 hours and 20 minutes.
532464
1 1/4 = 2 1/2 * 1/2\n\n2 1/2 * 60 = 150\n\n150 miles
1802
As I am travelling with a velocity 90 kph & the other car with 120 kph, I will appear as going back to the other driver but with a slower speed ie\na) 120-90 =30 kph\n\nThe other car wil appear to move ahead of me but with a slower speed as I am also chasing it\nb)120-90 =30 kph\n\nBut as we are talking about velocity we have to consider direction also. Hence my velocity will be -ve i.e. (-30 kph) & other car will be +30 kph
382721
The time taken is (200 miles divided by 185 mph) plus 5 minutes.  Divide 200 miles by that time to get the average speed.  Obviously, it's going to be less than 185 mph by around 1/12th