• Support PF! Buy your school textbooks, materials and every day products Here!

Equations for Accelerated Motion 4

  • Thread starter Medgirl314
  • Start date
  • #1
561
2

Homework Statement


A motorcycle traveling at 30 m/s comes to a stop over a distance of 150 m. What was the motorcycle's acceleration?


Homework Equations


v^2=vinitial+2aΔx


The Attempt at a Solution


I tried plugging in what I know.

0=900+2a*150 m

Then I divided 150 m and 900 by 150:

0=6+2a

This yields an answer of -4. It doesn't seem right, but I can't place why. I think I may have needed to divide the v^2 by 150, but that's 0/150, which wouldn't make sense. Thanks in advance for a reply!
 

Answers and Replies

  • #2
199
15

Homework Statement


A motorcycle traveling at 30 m/s comes to a stop over a distance of 150 m. What was the motorcycle's acceleration?


Homework Equations


v^2=vinitial+2aΔx


The Attempt at a Solution


I tried plugging in what I know.

0=900+2a*150 m

Then I divided 150 m and 900 by 150:

0=6+2a

This yields an answer of -4. It doesn't seem right, but I can't place why. I think I may have needed to divide the v^2 by 150, but that's 0/150, which wouldn't make sense. Thanks in advance for a reply!
does it?....check your final equation, you have done the rest of it correctly....it should be -ve because of deceleration (retardation), it just shows acceleration acts in direction opposite to its initial velocity

##0=6+2a##
##a=-3##

Edit: I think it was a typo, but this is what the equation is v^2=(vinitial)^2+2aΔx.....your calculations are correct except the very end of it.!!!
 
Last edited:
  • #3
561
2
Oh! Okay. I made a mistake in the post, I actually thought it was -2 m/s . I see what you did there, I added in my head instead of dividing. The main reason I thought it was wrong didn't have a reason. It just seemed like it should be different because I couldn't place how an acceleration of -2 or -3 would be enough to slow the car, but now that I look again, it makes sense. Thank you for a polite and helpful reply!
 
  • #4
561
2
The car?? I meant the motorcycle. Sorry. Blame it on lack of coffee syndrome.
 
  • #5
199
15
Oh! Okay. I made a mistake in the post, I actually thought it was -2 m/s . I see what you did there, I added in my head instead of dividing. The main reason I thought it was wrong didn't have a reason. It just seemed like it should be different because I couldn't place how an acceleration of -2 or -3 would be enough to slow the car, but now that I look again, it makes sense. Thank you for a polite and helpful reply!
no problem!!!.........just to make it seem reasonable you can use ##v=v_{0}+a.t##, solving for time gives ##10~seconds##. It doesn't stop immediately, it slowly decelerates therefore time is comparatively large and so is the distance. I hope this makes more sense now!!!!
 
  • #6
199
15
The car?? I meant the motorcycle. Sorry. Blame it on lack of coffee syndrome.
I got that, no problem.
 
  • #7
561
2
It does! Thanks, you have given some of the nicest replies I have found on here. If you have a moment, maybe you would go to my other Equations for Accelerated Motion problems and check those?

Thanks again!!
 
  • #8
561
2

Related Threads on Equations for Accelerated Motion 4

  • Last Post
Replies
4
Views
2K
Replies
0
Views
1K
  • Last Post
Replies
11
Views
1K
Replies
2
Views
683
Replies
1
Views
1K
  • Last Post
Replies
2
Views
3K
  • Last Post
2
Replies
38
Views
3K
  • Last Post
Replies
3
Views
2K
Replies
24
Views
212
Replies
2
Views
1K
Top