Physics Work question

[dellcom]

Im just a little stumped here.

the question is:

 

The position of a 2 kg particle moving in the x-y plane varies as a function of time according to the expression r = [(6t+1)m]i + [(-5t^2 +8t +3)m]j

 

Find the work done on the particle between t=1s and t=5s.

 

So i evaluated r for r(5)-r(1) and came up with R = 24i - 88j

Now to me it looks as if the only force will be in the y direction as that is the only place there is acceleration. so i figured 2kg * -9.8m/s^2 = -19.6j N

So i did the dot product of 24i - 88j * 19.6j = 1724.8J

However the answer is 1760J and I can not account for the discrepancy.

 

Any help would be appreciated

--pete

[dellcom]

any help?

[Jay-qu]

Work is Energy, force applied over a distance. For this you need acceleration. Well since you have a function of position you should know how to find the acceleration from that :)

 

Let us know how you go from there.

[dellcom]

ok i just did that and it works perfect because my prof used -10m/s^s as acceleration i was assuming gravity amazing what two tenths can do lol

 

thnx

[ghoghnus]

hello dear master plase help me about making redshift for thermal wavlenghat by simple matterial for visibele it on ccd camera.

[Jay-qu]

Hi ghoghnus, you may want to start a new thread about your questions and also reformulate them because I wasnt able to make heads or tails of them..

 

Jay