MHB 2-3 How much longer does it take?

  • Thread starter Thread starter karush
  • Start date Start date
AI Thread Summary
Driving from San Diego to Los Angeles at an average speed of 105 km/h takes 2 hours and 20 minutes, covering a distance of 245 km. When driving at a reduced speed of 70 km/h due to heavy traffic, the trip duration increases to 3.5 hours. This results in an additional travel time of 1 hour and 10 minutes compared to the faster speed. The calculations confirm that the distance remains consistent regardless of speed changes. Understanding these time differences is crucial for planning trips effectively.
karush
Gold Member
MHB
Messages
3,240
Reaction score
5
You normally drive on the freeway between San Diego and Los Angel es at an average speed of $105 \, km/h \, (65 \, mi/h)$ and the trip takes $2h$ and $20 \, min$
On a Friday afternoon, however, heavy traffic slows you down and you drive the same distance at an average speed of only
$70 km/h \, (43 mi/h)$
How much longer does it take?
$d_1=r_1t_1=\dfrac{65\,mi}{\cancel{ h }} \cdot 2.33\, \cancel{h}=151.45\,mi$
$t_2=\dfrac{d_1}{r_2}=151.45\,\cancel{mi}\cdot\dfrac{h}{43\,\cancel{mi}}=3.52\,h$
$t_\Delta=t_2-t_1=3.52h-2.33h\approx 1.19\, h \approx 1\, h\, 10\, min$

ok I still get ? with these word problems so...hopefully
 
Mathematics news on Phys.org
Driving at 105 km/hr it takes 2 hours and 20 minutes= 2 and 1/3 hours= 7/3 hours to drive from San Diego to Los Angeles. So how far is it from San Diego to Los Angeles? How long will it take to drive from San Diego to Los Angles at 70 km/h?
 
Since this has been here a week now without any more response:

It takes 7/3 hours to drive at 105 km/h between San Diego and Los Angeles so they are (7/3)(105)= 7(35)= 245 km apart.

If, instead, you drive at 70 km/h it will take 245/70= 3.5 hours or 3 hours and 30 minutes. That is one hour and ten minutes longer.
 
Suppose ,instead of the usual x,y coordinate system with an I basis vector along the x -axis and a corresponding j basis vector along the y-axis we instead have a different pair of basis vectors ,call them e and f along their respective axes. I have seen that this is an important subject in maths My question is what physical applications does such a model apply to? I am asking here because I have devoted quite a lot of time in the past to understanding convectors and the dual...
Insights auto threads is broken atm, so I'm manually creating these for new Insight articles. In Dirac’s Principles of Quantum Mechanics published in 1930 he introduced a “convenient notation” he referred to as a “delta function” which he treated as a continuum analog to the discrete Kronecker delta. The Kronecker delta is simply the indexed components of the identity operator in matrix algebra Source: https://www.physicsforums.com/insights/what-exactly-is-diracs-delta-function/ by...
Back
Top