# Homework Help: Velocity problem NEED HALP !

1. Jan 19, 2006

### zacazac33

velocity problem!! NEED HALP ASAP!

hellloooo physics friends ok heres the issue:

A 3000-lb. car has an engine which can deliver 80-hp. to the rear wheels. What is the max velocity at which the car can climb a 15-degree hill?

We were told this must be answered tomorrow for part of our final, and I absolutely have no idea what to do. Help would be greatly appreciated!

-zac

2. Jan 20, 2006

### Hootenanny

Staff Emeritus
Are you sure it is velocity and not acceleration?

3. Jan 20, 2006

### chroot

Staff Emeritus
The velocity up the hill specifies a certain change in evelation per unit time.

Change in gravitational potential energy can be defined in terms of change in evelation. Since you know how fast the elevation is changing, you know how fast the gravitational potential energy is changing.

Energy per unit time is power.

To keep the car moving at a steady velocity up the hill, the engine is converting energy in the fuel into increasing gravitational potential energy at a rate of 80 hp, or about 60 kJ/s: http://www.google.com/search?hl=en&q=80+hp+in+joules/second&btnG=Google+Search

All you have to do is figure out what rate of elevation gain would require 60kJ/s to maintain.

- Warren