I am working on a homework problem in my high school physics class, and I'm stuck on a simple problem. Hopefully someone can help. Here's the question.
Ernie and Burt take off from the same point in their individual cars traveling in the same direction along a straight highway. Ernie travels at 75 miles/hour and Burt travels at 60 miles/hour. How much sooner does Ernie arrive at a destination 10 miles away. How far must Ernie travel before he has a 15 minute lead on Burt?
Thank you for the help!
2006-09-15 07:28:22 · 8 answers · asked by Lisa O 1 in Science & Mathematics ➔ Physics
1. Ernie 75 mph = 75/60 = 1.25 miles/minute
Burt 60mph = 60/60 = 1 miles/minute
For 10 miles Ernie takes 10/1.25 = 8 minutes
For 10 miles Burt takes 10/1 = 10 minutes
Therefore Ernie gets there 2 minutes sooner.
2. If he goes m miles to establish the lead then
m/1 - m/1.25 = 15 minutes
1.25m - 1m = 15x1.25x1
0.25m = 18.75
18.75/0.25 = 75 miles for a lead of 15 mins
The key is to convert miles per hour into miles per minute. It makes the reasoning easier.
2006-09-15 07:40:39 · answer #1 · answered by Sarah1975 2 · 0⤊ 0⤋
You have two parts to this problem, each consisting of a simple time/distance/velocity problem.
E. is doing 75 MPH so given a distance of 10 miles he will take 10/75 hours (Convert to minutes...)
B is doing 60 MPH so will take
10/60 hours (Convert to minutes).
Subtract one from the other.
For the second part E is moving 15MPH faster then Burt and Burt is moving at 1 mile per minute.
Thus a 15 minute lead is 15 miles and given that E is moving 15MPH faster then burt that will take him how long to build up?
For added credit, how far down the road will E be when he is 15 minutes ahead (Trivial)?
HTH.
Regards, Dan.
2006-09-15 07:47:25 · answer #2 · answered by Dan M 3 · 0⤊ 0⤋
time taken=distance /time
time taken by Emie for 10 miles @75 mph=10/75=8 min
time taken by Burt 10/60=10 min
Emie will ariive 2 min sooner
2.let him travel x miles
the equation is x/60-x/75=1/4
The LCD is 300
5x-4x=300/4
therfore x=75 miles
Emie has to cover 75 miles to take a lead of 15 mts
2006-09-15 07:42:28 · answer #3 · answered by raj 7 · 0⤊ 0⤋
since the destination is 10 miles, Burt gets there in 10 min and Ernie in 7.5 - so 2.5 minutes ahead.
60 miles before he has a 15 minute lead.
2006-09-15 07:37:57 · answer #4 · answered by ever_curious 3 · 0⤊ 1⤋
ernies time=(75/60)/10(s/v)
= 8 mins sooner.
ernies S=15*(75/60)(V*t)
=18.75 miles
2006-09-15 08:14:16 · answer #5 · answered by tonima 4 · 0⤊ 0⤋
Emie has to cover 75 miles to take a lead of 15 mts
2006-09-15 08:02:36 · answer #6 · answered by Johan S 1 · 0⤊ 0⤋
the object does have a uniform acceleration of 0 however the respond "uniform acceleration" probable isn't particular sufficient to be ultimate. it would be be greater ultimate to declare that the object has a relentless velocity via fact the slope of the rate as against time graph is 0 and subsequently acceleration is 0. If there became a selection of "consistent velocity" or "uniform velocity" those selections may be the ultimate answer in a dissimilar determination question.
2016-10-15 00:56:53 · answer #7 · answered by ? 4 · 0⤊ 0⤋
2 mins
second part not so sure. 15 miles?
2006-09-15 08:44:01 · answer #8 · answered by jaco 3 · 0⤊ 0⤋