A train covers 60 miles between 2pm - 4 pm. How fast was it going at 3pm?
回答 (47)
2015-10-19 10:47 am
We don't know because there is not enough information. Did the train stop on the way? Was it stationary at 3:00 pm? Did it travel fast on straight stretches and have to slow down for a bed at 3:00pm? There are many possibilities and we just don't know.
Even if we add some suppositions, like the train accelerated and slowed down at the same rate and that, apart from at those time, it travelled at a constant speed, we still can't say what the speed would have been at 3:00 because we don't know the rate of acceleration/deceleration.
A simple answer would be that, if the train covered 60 miles in 2 hours, then it was travelling at 30 MPH at 3:00pm .... but, unless the train was already up to speed before and after the measured 60 miles and unless we KNOW the train maintained a constant speed, we cannot be sure the speed at 3:00pm was 30 MPH.
Even if we add some suppositions, like the train accelerated and slowed down at the same rate and that, apart from at those time, it travelled at a constant speed, we still can't say what the speed would have been at 3:00 because we don't know the rate of acceleration/deceleration.
A simple answer would be that, if the train covered 60 miles in 2 hours, then it was travelling at 30 MPH at 3:00pm .... but, unless the train was already up to speed before and after the measured 60 miles and unless we KNOW the train maintained a constant speed, we cannot be sure the speed at 3:00pm was 30 MPH.
2015-10-19 2:07 pm
Unknown.
It could have gone 60 mph between 2 and 2:30, stopped between 2:30 and 3:30, and gone 60 mph between 3:30 and 4.
If we had been told that it was going at a CONSTANT SPEED FOR THE ENTIRE TIME, then it would be a different story.
It could have gone 60 mph between 2 and 2:30, stopped between 2:30 and 3:30, and gone 60 mph between 3:30 and 4.
If we had been told that it was going at a CONSTANT SPEED FOR THE ENTIRE TIME, then it would be a different story.
2015-10-19 1:51 pm
You can only say the train's average speed was 30 MPH. Now, if you were told the train ran at a constant speed, that would also be it's speed at any time. Otherwise the answer could be anything between 0 and the maximum sped of the train. You cannot extract more information from the data beyond that which is provided.
2015-10-22 1:56 am
You can only say the train's average speed was 30 MPH. Now, if you were told the train ran at a constant speed, that would also be it's speed at any time. Otherwise the answer could be anything between 0 and the maximum sped of the train. You cannot extract more information from the data beyond that which is provided.
2015-10-19 10:34 am
You know the average speed during the two hour increment :
------------------------------------------------------------------------------
vbar = d / t = ( 60 mi ) / ( 2 hr ) = 30 mph
NOTE:
-----------
You do not have enough information to get the speed at 3:00 pm <--------------
There are many distributions of speed versus time that will give vbar = 30 mph.
Please award Best Answer to the most helpful response to your question.
------------------------------------------------------------------------------
vbar = d / t = ( 60 mi ) / ( 2 hr ) = 30 mph
NOTE:
-----------
You do not have enough information to get the speed at 3:00 pm <--------------
There are many distributions of speed versus time that will give vbar = 30 mph.
Please award Best Answer to the most helpful response to your question.
2015-10-19 3:56 pm
Nobody can tell
2015-10-19 12:01 pm
You simply cannoy tell.
2015-10-19 10:32 am
so 60 = miles in 2 hours so that easy to say it is traveling at 30 miles per hour. So 3pm is half way between 2mp & 4pm so the train has been travelling for 1 hour at 3pm so the answer must be 30mph.
2015-10-22 8:05 pm
The only information given is the total duration and the total distance.
Using the formula Distance = Rate x Time, or d=rt, we have 60 miles = r*2 hrs, or r = 60/2 miles/hr, or r = 30 mph.
This gives us the average rate of speed over the 2 hours, or 30 mph. We do not know the instantaneous speed at any given time, but can assume that it is 30 mph or at least close to that, since we were not given any information that the train stopped, sped up, or slowed at any given time.
Using the formula Distance = Rate x Time, or d=rt, we have 60 miles = r*2 hrs, or r = 60/2 miles/hr, or r = 30 mph.
This gives us the average rate of speed over the 2 hours, or 30 mph. We do not know the instantaneous speed at any given time, but can assume that it is 30 mph or at least close to that, since we were not given any information that the train stopped, sped up, or slowed at any given time.
2015-10-22 5:45 am
on average that train traveled with a speed of 30 miles per hour, however it could of moved faster in that time and then slower but the answer is 30 miles per hour. This is because:
it traveled 60 miles in 2 hours (4pm - 2pm = 2hours) so
speed = distance divided by time
then
speed = 60/2 = 30 miles per hour
it traveled 60 miles in 2 hours (4pm - 2pm = 2hours) so
speed = distance divided by time
then
speed = 60/2 = 30 miles per hour
2015-10-21 2:19 am
The question does not provide enough info to tell that, it could have been stopped at 3 PM for all we know.
2015-10-20 4:34 am
You can say that it is 30 mph because 60/2 = 30. It may not be the
correct answer because we are not told that the train travels at a constant
rate.
correct answer because we are not told that the train travels at a constant
rate.
2015-10-20 12:10 am
Did it stop at any point?
2015-10-19 10:26 am
30 mph
2015-10-19 10:26 am
30 mph. At all times incidentally.
2015-10-25 8:06 pm
IFF (thats a term for "If, and only If"), the train is going at a constant speed, then 60 miles in 2 hrs, means 30 miles in 1hour, ie. 30mph
However, the question doesnt say "constant speed", so theoretically, the train could sit in one place with the driver & crew drinking coffee, discussing politics and checkin facebook etc, from 2pm untill 3:55:40pm, and shoot off at mach 1 (supersonic) and cover 60 miles in the remaining 4min40sec and still have technically covered "60 miles between 2 & 4 pm".
If this question was a direct quote from a homework, Id point this out...and demand marks...! :-)
However, the question doesnt say "constant speed", so theoretically, the train could sit in one place with the driver & crew drinking coffee, discussing politics and checkin facebook etc, from 2pm untill 3:55:40pm, and shoot off at mach 1 (supersonic) and cover 60 miles in the remaining 4min40sec and still have technically covered "60 miles between 2 & 4 pm".
If this question was a direct quote from a homework, Id point this out...and demand marks...! :-)
2015-10-25 4:03 am
My guestimation would be around 40 mpr. As at that speed here most derail. Then gained speed from there rolling down the mountain side. To average 30 mpr.
2015-10-24 5:37 pm
30 miles per hour
2015-10-23 1:42 am
Average of 30.
2015-10-23 12:56 am
30. If you want the method, here it is: 60 ( # of miles ) divided by 2 ( # of hours ) = 30 0r 30 mph. I hope you understand.
2015-10-22 8:40 pm
the problem with your question is that it does not show us enough information about the train motion at every hour or time unit, you can say it's 30 mph but with the information we got we can't comprehend an entire course for the train motion so we can't find it's instantaneous speed at a specific unit of time during it's motion.
參考: general physics class.
2015-10-22 10:04 am
It could be standing still at that time. Who knows?
2015-10-21 3:32 pm
0 because he stopped at your sisters house to get laid. stop asking stupid questions.,
2015-10-21 10:08 am
60 miles
2015-10-21 7:03 am
30 mph
2015-10-21 3:00 am
I believe there was a steep hill around about that time, Just before we stopped to take on water at petticoat junction. That ole gal took a good 15-20 minutes to get her up to 88 miles per hour.
2015-10-21 6:43 am
There is no way to know, because 60/2 is 30 mph, which is an average. At any given moment, such as 3 pm, it could be instantaneously traveling at any speed, as long as it resulted in that average.
2015-10-21 6:07 am
30
2015-10-19 2:25 pm
I say 30 miles per hour.
2015-10-21 4:02 am
60 BECAUSE U SAID BETWEEN...........
2015-10-20 9:48 pm
30 MPH
2015-10-20 10:13 am
30mph
2015-10-20 7:35 am
60/3=30
The Answer Is 30.../@/..
The Answer Is 30.../@/..
2015-10-20 6:37 am
30mph
2015-10-19 3:21 pm
2hr to 3hr
3hr to 4hr
AS 2HR TO 4HR IT COVERS 60 MILES SO 2HR TO 3HR IT COVERS HALF OF THE MILES (i,e) 30 mph
3hr to 4hr
AS 2HR TO 4HR IT COVERS 60 MILES SO 2HR TO 3HR IT COVERS HALF OF THE MILES (i,e) 30 mph
2015-10-19 12:27 pm
30 mph
2015-10-19 11:24 am
30mph
2015-10-20 10:07 pm
30
2015-10-20 2:03 pm
30
2015-10-19 8:44 pm
30 mph
2015-10-19 4:19 pm
30 MPH
2015-10-19 11:21 am
S = D/T
S = 60/2
S = 30
S = 60/2
S = 30
2015-10-20 7:07 pm
At an average speed of 30 mph at 3 pm , between 2pm to 4pm totally covering 60 miles
2015-10-19 11:27 pm
30 mph
2015-10-19 1:25 pm
30 mph
2015-10-20 5:20 am
30
2015-10-19 11:51 pm
30
收錄日期: 2021-04-18 13:57:36
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https://hk.answers.yahoo.com/question/index?qid=20151019022452AAjJnoK