+0  
 
0
1029
7
avatar+105 

A car starts out going 17.88m/s and 10 seconds later is going 26.82m/s. what is its acceleration in mi/hr²?

 Jul 2, 2014

Best Answer 

 #6
avatar+33603 
+10

You need to be careful with units here.  The first question asks for the answer in miles/hr2; the answer is given in m/s2.

The second example finds the difference in speeds given in miles/hr and divides by seconds, so the value given has units of miles/(hr.sec).

 Jul 3, 2014
 #1
avatar+576 
+10

acceleration is change in velocity divided by time.  In 10 seconds the change in velocity is 26.82-17.88=8.94

then we divide by time, 10, to get .894m/s^2

 Jul 2, 2014
 #2
avatar+105 
0

thanks! whats the formula for deceleration? i have driving at 25mi/hr slam on breaks, and in 3 seconds speed decreases to 8mi/hr.

 Jul 2, 2014
 #3
avatar+576 
+5

deceleration and acceleration are exactly the same thing!  The only difference is that if you lose speed your resulting acceleration will be negative.  In your example

(8-25)/3=-17/3

 Jul 2, 2014
 #4
avatar+105 
0

Much appreciated! 

 Jul 2, 2014
 #5
avatar+118587 
+5

This is AVERAGE acceleration of course.

 Jul 3, 2014
 #6
avatar+33603 
+10
Best Answer

You need to be careful with units here.  The first question asks for the answer in miles/hr2; the answer is given in m/s2.

The second example finds the difference in speeds given in miles/hr and divides by seconds, so the value given has units of miles/(hr.sec).

Alan Jul 3, 2014
 #7
avatar+118587 
0

Yes, I didn't notice that thank you Alan.

 Jul 3, 2014

0 Online Users