## anonymous one year ago I'm so confused can someone help?? The driver of a pickup truck going 120 km/h applies the brakes, giving the truck a uniform deceleration of 5.00 m/s2 while it travels 35.0 m. How much time has elapsed?

1. anonymous

|dw:1442519392779:dw| this is about as far as I could get...I have no idea where to go with this

2. anonymous

Reverse the acceleration formula

3. anonymous

a=v/t?

4. anonymous

Wait nvm completely read that wrong, sorry dislexia. But can't help out, not there yet

5. anonymous

oh...lol thanks for trying :)

6. YumYum247

Given: Vi = 120Km/hr, a = 5m/sec^2, dh = 35m Variables not given: Vf Required: t USe the d= Vi X t + 1/2(a X t^2) and solve for "t"

7. YumYum247

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8. YumYum247

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9. YumYum247

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10. YumYum247

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11. YumYum247

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12. YumYum247

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13. YumYum247

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14. YumYum247

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15. YumYum247

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16. YumYum247

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17. anonymous

can you slow down and explain some of these? I don't really understand. like in the 2nd photo where are you getting the 5 you're diving by?

18. YumYum247

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19. YumYum247

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20. anonymous

can you please explain what you are doing....

21. YumYum247

hold up i'm a lil stuck...LOL

22. YumYum247

oh i got it....i didn't quite read "deceleration...a = -5m/sec^2

23. YumYum247

|dw:1442522102414:dw| Restart!!!! :"D

24. YumYum247

there should have been a negative sign in front of the -2.5 that i forgot to put,....

25. YumYum247

i'll explain just hold on....

26. anonymous

lol maybe try using the equation tool instead of the drawing tool

27. YumYum247

cuz i can....|dw:1442522842144:dw|

28. YumYum247

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29. YumYum247

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30. YumYum247

|dw:1442523188249:dw|

31. YumYum247

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32. YumYum247

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33. YumYum247

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34. YumYum247

t= -33.3 + 27.54/-5 t= -5.76/-5 t=1.152sec

35. YumYum247

i'm out!!!!

36. YumYum247

Always remember this trick....identify your variables... see what's given to you and what isn't and what is required..... in this case. They gave us the acceleration, initial velocity and horizontal distance. but they didn't tell us the final velocity and asked you to find the time...this is where you need to use a little trick, use the formula for which the variable isn't given...

37. YumYum247

in this case, fnal velocity.

38. YumYum247

39. YumYum247

and solve for the "T". you should get a quadratics expression.....t = m/sec^2T^2 + m/secT -horizontal distance(35m) use the quadratics formula to solve for time....

40. YumYum247

get it? O_O

41. YumYum247

ii'm getting late. do some question and hope for the best!!! :"D later!!!!!!!