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Acceleration equations involving time.

  • Thread starter cneedshelp
  • Start date
  • #1
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At highway speeds, a certain car is capable of an an acceleration of about 1.7 m/s^2. At this rate, how long does it take to accelerate from 90 km/hr to 110 km/hr? (WATCH UNITS.)

Given- Time=?
A=1.7m/s^2
Vi=90km/hr
Vf=110km/hr


Vf=vi+at Solve for t! T= vf-vi/a 110km/hr-90km/hr = 20km/hr
1.7m/s^2

How do I divide 20km/hr by 1.7 m/s^2?
 

Answers and Replies

  • #2
461
8
At highway speeds, a certain car is capable of an an acceleration of about 1.7 m/s^2. At this rate, how long does it take to accelerate from 90 km/hr to 110 km/hr? (WATCH UNITS.)

Given- Time=?
A=1.7m/s^2
Vi=90km/hr
Vf=110km/hr


Vf=vi+at Solve for t! T= vf-vi/a 110km/hr-90km/hr = 20km/hr
1.7m/s^2

How do I divide 20km/hr by 1.7 m/s^2?
First convert your units to be in terms of meters and seconds then do the calculation.
 
  • #3
14
0
First convert your units to be in terms of meters and seconds then do the calculation.
I got .02m but i'm not sure how to convert the hr to seconds
 
  • #4
461
8
I got .02m but i'm not sure how to convert the hr to seconds
What is that .02m?
You want to convert km/hr to m/s.An hour has 60 mins and a min has 60 sec.
[itex]\frac{1km}{hr}\frac{1hr}{3600s}\frac{1000m}{1km}= \frac {1000m}{3600s}[/itex]
 
  • #5
14
0
What is that .02m?
You want to convert km/hr to m/s.An hour has 60 mins and a min has 60 sec.
[itex]\frac{1km}{hr}\frac{1hr}{3600s}\frac{1000m}{1km}= \frac {1000m}{3600s}[/itex]
What I did now was 20(1000)/3600
is 6m/s using sig figs and thats the answer! right?
 
  • #6
461
8
What I did now was 20(1000)/3600
is 6m/s using sig figs and thats the answer! right?
Yes if your teacher requires you to round up after every step.I would round after the final answer for time though.
 

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