Work question without distance, work and velocity

In summary: I have d=vt + 1/2at^2d=vt + 1/2at^2Yes! :smile:This is the one we need.Can you use it to calculate the distance?I will show you how I set it up...vt+(1/2)(-7.5)(2)^2---You've left off the initial velocity uSo it is: u=0v= u + at= 0 + 7.5*2= 15Correct so far?Yes! :smile:So now you can fill in d=vt+(1/2)at^2 asd= 0*2 + 1/
  • #36
You are impatient, aren't you? ;)

MsHomework said:
Ok well I decide to just do v=at. then I did velocity final= velocity initial + (acceleration)(distance). Which gave me the initial velocity of 15m/s. Lastly I did the d= 1/2 (velocity initial + velocity final)t equation which gave me a distance of 15 m. is this right?

What you write here is incorrect.
Surprisingly you do have the right answer for the distance.

The proper formula is:
distance = (velocity initial) (time) + (1/2) (acceleration) (time)^2.
MsHomework said:
Finally after that when I replaced the distance i got into the work equation, I got 900J. Is this right

Yes, this is right.

I was leading up to the trick that accelerating for 2 seconds from rest covers the same distance as decelerating in 2 seconds to rest.
I guess that won't be necessary any more.
 
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  • #37
YUS! I UNDERSTAND NOW! Thank you for helping me! I will be posting another question soon, check it out!
 
  • #38
I hope you realize that velocity has to be in the direction the object is moving since it is the time rate of change of directed distance so no velocity cannot be in the direction opposite to its motion
 

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