# Another physics problem? (sorry so many at one time)

1. Sep 12, 2009

### kashiark

1. The problem statement, all variables and given/known data
After a day of testing race cars, you decide to take your own 1550 kg car onto the test track. While moving down the track at 10 m/s, you uniformly accelerate to 30 m/s in 10 s. What is the average net force that the track has applied to the car during the 10 s interval?

2. Relevant equations
F=ma

3. The attempt at a solution
Is it just (20/10)*1550? the only thing that confuses me is "the average net force that the track has applied to the car." The track applied to the car. Did the track apply the force?

2. Sep 12, 2009

### kuruman

Your calculation is correct. Yes, the track applied the force. What else is there (not part of the train) that could provide a horizontal force? Or, if the track were completely frictionless, i.e. cannot provide a horizontal force, would the train be able to accelerate?

3. Sep 12, 2009

### kashiark

If the dragster moves like a squid :) Sorry, I couldn't resist, but seriously, thanks!

4. Sep 12, 2009

### kuruman

Sorry, dragster not train. Rocket-propelled dragsters do act like squids, so your comment is not as silly as you might think.