# Homework Help: Entering a Freeway

1. Jun 25, 2006

### Musicman

Entering the Freeway. A car sits in an entrance ramp to a freeway, waiting for a break in the traffic. The driver sees a small gap between a van and an 18-wheel truck and accelerates with constant acceleration along the ramp and onto the freeway. The car starts from rest, moves in a straight line, and has a speed of 30 m/s (67 mi/h) when it reaches the end of the 115 m long ramp.

Ok for the acceleration I got 3.91 m/s/s and got that it takes 7.61 s for the car to travel the length of the ramp, but I dont understand part C:

(c) The traffic on the freeway is moving at a constant speed of 30 m/s. What distance does the traffic travel while the car is moving the length of the ramp?

i got 117.4 m but idk

2. Jun 25, 2006

### Hootenanny

Staff Emeritus
These are both correct, however I think you have induced a rounding error, the time should be 7.67s
I'm afraid this is not correct. Don't forget the traffic is travelling at a constant velocity.

3. Jun 25, 2006

### Musicman

what did u get then? cuz im totally lost like i knew what i was doing for the first 2 parts but not this part.

4. Jun 25, 2006

### Hootenanny

Staff Emeritus
I'm not giving you the answer :tongue2: . Think about traveling at constant velocity. What is the equation for uniform velocity? How do you define velocity?

5. Jun 25, 2006

### Musicman

x=v of x times t

6. Jun 25, 2006

### Hootenanny

Staff Emeritus
Thats right, distance is equal to the product of velocity and time. Use it

7. Jun 25, 2006

### Musicman

well i put 29.75 and it said its wrong and it was my last submission so oh well, apparently 7.61 times 3.91 doesnt work.

8. Jun 25, 2006

### Hootenanny

Staff Emeritus
3.91 is the acceleration of the car travelling up the ramp not the velocity of the cars travelling on the freeway which would be 7.66 x 30 = 230m