# Homework Help: Question how to solve car problem!

1. May 2, 2004

### jaye21

Hi all, I am not sure if this is the right place to post this as I am new to the boards. So sorry if it is not.

I received a bunch of HW assignments for the weekend and I'm just not understanding some of the concepts. I was wondering if anyone could help start me off on a couple problem. Any help would be appreciated thanks!

The position of a 2kg 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 between t=1 and t=5. Determine the power delivered to the particle at t=3.

? now I know how to do this problem given a function in relation to force. but not as a function of time. given as a function of time do i just subtract r(5) from r(1), or do I still have to integrate?

? with the power i am just very confused.

A 1000 kg car racing up an 80 m-high mountain road runs out of gas at a height of 45 m while traveling at 25 m/s. Cleverly, the driver shifts into neutral and coasts onward. ( Neglect friction and use conservation of mechanincal energy).

? will he clear the 80 m peak, show work. not having brakes at what speed will he reach the bottom.

No idea where to start on this one. If anyone could teach me it is just homework and I want to kno how to do this before next class. Thank you!

2. May 2, 2004

### arildno

1. How are forces that act on an object related to the acceleration of the object and how is the acceleration of the object related to the position of the object?
These are the first 2 questions you should try to answer.